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Z OLD Molecules, Genes and Disease > Protein Targetting > Flashcards

Protein Targetting Flashcards

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1
Q

When is a protein synthesised by a ribosome attached to the ER membrane?

A

If the protein is destined for the membrane or secretory pathway via co-translational insertion

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2
Q

What happens to the proteins as they are synthesised when the ribosome is attached to the ER membrane?

A

They are inserted into the lumen

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3
Q

When are proteins synthesised to completion in the cytoplasm?

A

If the protein is destined for the cytosol, or post-translational import into organalles

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4
Q

What organelles may receive proteins from post-translational import?

A
  • Mitochondria
  • Nucleus
  • Peroxisomes
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5
Q

What are the requirements for protein sorting?

A
  • Signal
  • Receptor
  • Translocation machinery
  • Energy
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6
Q

Where is the signal for protein sorting?

A

Intrinsic to the protein

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7
Q

What is the purpose of the receptor in protein sorting?

A

Recognises the signal, and directs it to the correct membrane

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8
Q

What is the energy needed for in protein sorting?

A

To transfer the protein to it’s new place

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9
Q

Where is the signal usually located if the protein target is the ER?

A

Usually at the N-terminus

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10
Q

What eventually happens to the signal if the protein target is the ER?

A

It is removed

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11
Q

What is the signal when the protein target is the ER?

A

6-12 hydrophobic amino acids, often preceded by 1 or more basic amino acids

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12
Q

Where is the signal usually located when the protein target in the mitochondrial matrix?

A

At the N-terminus

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13
Q

What eventually happens to the signal if the target is the mitochondrial matrix?

A

It is removed

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14
Q

What is the signal when the target is the mitochondrial matrix?

A

An amphipathic helix of 20-50 residues with alternating R/K and hydrophobic sites

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15
Q

Where is the signal if the target is a peroxisome?

A

C-terminus

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16
Q

What eventually happens to the signal if the target is a peroxisome?

A

It remains

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17
Q

Usually, what is the signal if the target is a peroxisome?

A

S-K-L

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18
Q

Where is the signal if the target is the nucleus?

A

Internal- can be anywhere in the protein, but has to be exposed on the surface

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19
Q

What eventually happens to the signal when the target is the nucleus?

A

It remains

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20
Q

What is the signal when the target is the nucleus?

A

Either one cluster of 5 basic amino acids, or 2 smaller basic clusters separated by about ~10 amino acids

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21
Q

How is a protein imported into the mitochondrial matrix?

A
  • Protein with signal kept unfolded by chaperones
  • Signal binds receptor
  • Receptor delivers to important pore
  • Protein fed through pore in outer membrane
  • Protein moves through channel in adjacent inner membrane
  • Targeting signal cleaved, allowing protein to fold
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22
Q

What is required for chaperone proteins to bind to mitochondrial proteins?

A

ATP hydrolyssi

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23
Q

What does a pyruvate dehydrogenase deficiency result in?

A

A built up of lactic acid, and neurological problems

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24
Q

What causes pyruvate dehydrogenase deficiency?

A
  • Mutation at codon 10 in N-MTS of PDH E1å. subunit, resulting in an arg →pro substitution
  • Receptor can’t recognise targeting sequence
  • Reduced uptake into mitochondria
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25
Q

Why does the base substitution mean that the receptor can’t recognise the targeting sequence in PDH?

A

The helix breaking proline destabilises the helical N-MTS, and there is a loss of one basic residue on the hydrophobic face of the amphipathic helix

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26
Q

How does cargo get imported into the nucleus?

A
  • In the cytosol, importin binds cargo containing a nucleur localisation signal
  • Can then travel through nuclear pore
  • In nucleus, Ran-GTP binds to importin, causing a conformational change that displaces the cargo
  • Importin with bound Ran-GTP recycled to the cytoplasm
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27
Q

What is required to make Ran-GTP and release importin?

A

GTP hydrolysis

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28
Q

What can mutation of nuclear localisation signals lead to?

A
  • Swyer syndrome
  • Leri-Weill dyschondrosterosis
  • Langer mesomelicdysplasia
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29
Q

What causes Swyer syndrome?

A

A loss/mutation of NLS in sex determining region Y (SRY) protein, leading to an XY genotype, but outwardly female, as SRY type needed for testis differentiation

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30
Q

What causes Leri-Weill dyschondrosterosis and Langer mesomelicdysplasia?

A

R173C mutation of NLS of SHOX transcription factor, as SHOX required for skeletal development

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31
Q

How doesLeri-Weill dyschondrosterosis and Langer mesomelicdysplasia present?

A

Short stature

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32
Q

Describe the process of PTS-1 directed import of peroxisomal matrix proteins

A
  • In cytosol, peroxisomal import receptor binds cargo with PTS
  • Peroxisomal protein remains folded, and receptor integrates into translocon, thereby opening it, so whole peroxisomal protein can enter through channel
  • Peroxisome targeting sequence dissociates from the receptor
  • Receptor is returned to the cytosol
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33
Q

What is required for the returning of the PTS-1 directed import receptor to the cytosol?

A

ATP hydrolysis

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34
Q

What is meant by co-translational transport?

A

Proteins delivered as they’re being synthesised

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35
Q

Where does protein synthesis occur when the protein is destined for the ER/secretory pathway?

A

Bound ribosomes

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36
Q

Are proteins synthesised for the ER/secretory pathway soluble or membrane bound?

A

Can be either

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37
Q

Where are proteins synthesised on bound ribosomes synthesised into/across?

A

The ER membrane

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38
Q

What happens once a protein has been synthesised into/across the ER membrane?

A
  • Budding and fusion of ER-to-Golgi vesicles containing proteins to form cis-Golgi
  • Cisternal progression form cis-Golgi → medial-Golgi → trans-Golgi
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39
Q

What happens to proteins required by the ER?

A

There can be retrograde transport from the Golgi to the ER, and from later to earlier Golgi cisternae

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40
Q

Where does sorting occur?

A

In the trans-Golgi network

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41
Q

How can proteins be secreted?

A
  • Regulated secretion

- Constitutive secretion

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42
Q

What can happen to proteins not secreted?

A

Sorted into lysosomes

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43
Q

How are proteins sorted into lysosomes?

A

They bud off from the trans-Golgi network in a transport vesicle, then fuse with an endocytic vesicle to form a late endosome, which then turns into a lysosome

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44
Q

What is in endocytic vesicles?

A

Material to be broken down

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45
Q

What kind of cells tend to carry out regulated secretion?

A

Specialised cells;

  • Endocrine cells
  • Exocrine cells
  • Neurocrine cells
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46
Q

What do endocrine cells secrete?

A

Hormones

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47
Q

What do exocrine cells secrete?

A

Digestive enzymes

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48
Q

What do neurocrine cells secrete?

A

Neurotransmitters

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49
Q

Give an example of a polarised secretory cell

A

The pancreatic acinar

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50
Q

What is true of a polarised secretory cell?

A

It is very organised

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51
Q

How is a polarised secretory cell organised?

A

Golgi next to nucleus, secretory vesicles near apical surface of cell

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52
Q

Why is it important that products are secreted at apical surface, not basal, in a polarised secretory cell?

A

Because the cell is often secreting digestive enzymes

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53
Q

What are proteins with signal peptides attached termed?

A

Pre-

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54
Q

What happens once a pre- protein is cleaved?

A

It looses the term pre-

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55
Q

What cleave signal sequences?

A

Specific enzymes called signal peptidases

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56
Q

What do signal peptidases recognise?

A

Charged residues adjacent to signal sequences

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57
Q

What is a signal recognition particle (SRP)?

A

A multi-domain riboprotein

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58
Q

What does a SRP do?

A

Mediates 3-way association with SRP-receptor in ER, the ribosome and the signal peptide

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59
Q

What does a SRP particle consist of?

A

A single RNA molecule of ~300 bases long, in complex with 6 different proteins

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60
Q

How are the proteins in SRP named?

A

P(number), based on the proteins molecular weight

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61
Q

What does P54 in SRP do?

A

Binds to signal sequences present in secretory proteins

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62
Q

What do other proteins, for example P9 and P14, in SRPs do?

A

Important for interacting with ribosomes

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63
Q

Describe the process of synthesis of secretory proteins and their translocation across the ER membrane using SRPs

A
  • As protein synthesised, signal sequence protrudes from ribosome- is exposed.
  • SRP recognises protruding signal sequence, stopping translation
  • SRP binds to signal sequence, and is therefore attached to the ribosome
  • SRP is recognised by receptor present in ER membrane
  • Hydrolysis of GTP bound to the receptor and the SRP opens the translocon
  • Signal peptidase cleaves signal sequence in ER
  • Translation continues into ER lumen until finished
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64
Q

Why does the SRP stop translation?

A

To prevent synthesis in the cytoplasm, as it should be inserted into the secretory pathway

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65
Q

What is the receptor that binds to SRP composed of?

A

α and ß unit sub unit

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66
Q

What happens when a sub-unit of the receptor and a SRP has GTP bound?

A

It increases the affinity of a ribosome-SRP complex to receptor, and so binds easier

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67
Q

Why must the translocon remain closed when idle?

A

Otherwise important things such as calcium ions may leak out

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68
Q

What happens once translation is finished?

A

The ribosome detaches, the translocon closes and the folded protein is in the lumen

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69
Q

What is insertion into the ER membrane required for the delivery of?

A

Membrane proteins destined for plasma membrane or internal membrane of secretory pathway

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70
Q

What is the mechanism for delivery of N-terminal signal sequence to translocator the same as?

A

For a secretory pathway

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71
Q

What exists in the case of a type 1 membrane protein?

A

A second hydrophobic sequence

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72
Q

What is the purpose of the second hydrophobic sequence in a type 1 membrane protein?

A

To anchor the protein in the membrane, and prevents further transfer into the ER lumen

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73
Q

What is thesecond hydrophobic sequence in a type 1 membrane protein called?

A

A stop transfer anchor sequence

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74
Q

What happens once a stop transfer anchor sequence has been implanted into the membrane?

A

Synthesis continues in cytoplasm until a stop codon is reached

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75
Q

What are the functions of the endoplasmic reticulum?

A
  • Insertion of proteins into membranes
  • Specific proteolytic cleavage
  • Glycosylation
  • Formation of S-S bonds
  • Proper folding of proteins
  • Assembly of multi-subunit proteins
  • Hydroxylation of selected Lys and Pro residues
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76
Q

What is glycosylation of proteins important?

A
  • Correct protein folding
  • Protein stability
  • Facilitates interactions with other molecules
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77
Q

What may happen to protein stability without glycosylation?

A

Half life may be reduced

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78
Q

What can happen if theres deficiencies in N-linked glycosylation?

A

Severe human diseases

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79
Q

Where are sugars added in N-linked glycosylation?

A

Sugars are added on a asparagine side chain

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80
Q

What does the glycosylation reaction involve?

A

An amino group

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81
Q

Can every asparagine be glycosylated?

A

No, needs to be [X]-[Ser/Thr]

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82
Q

Why does the asparagine need to be[X]-[Ser/Thr] to be glycosylated?

A

To be recognised by the enzyme that transfers oligosaccharides

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83
Q

How are oligosaccharides made?

A

Assembled in ER on lipid carrier, then transferred to asparagine on growing protein

84
Q

What does the oligosaccharide consist of?

A

3 glucose, 9 mannose and 2 N-acetylglucosamine

85
Q

Where does glycosylation occur?

A

In ER

86
Q

Where is the oligosaccharide preassembled?

A

A lipid carrier (dolichol)

87
Q

What happens once the oligosaccharide has been transferred onto the protein?

A

Extensive modification in the ER and Golgi, by trimming and addition of further sugars

88
Q

What do peptidyl-prolyl isomerases do?

A

Accumulate the interconversion of cis and trans isomers of proline residues

89
Q

Why is proline different from other amino acids?

A

It has a rigid structure

90
Q

Where can proline rotate?

A

Around the peptide bond

91
Q

What is the result of the ability of proline to rotate around the peptide bond?

A

Gives rise to cis and trans forms

92
Q

When does the interconversion of cis and trans proline need to occur?

A

During the folding reactions in a number of proteins, particularly IgGs

93
Q

Why are peptidyl-prolyl isomerases useful industrially?

A

They greatly facilitate rapid protein folding

94
Q

What is formed when 2 thiol side chains are oxidised?

A

Disulphide bonds

95
Q

Give the equation for the formation of disulphide bonds?

A

-SH + HS- → -S-S- + 2e - + 2H +

96
Q

Where is disulphide bond formation important?

A

Holding sub-units together, and correct folding of proteins

97
Q

What catalyses the formation of disulphide bonds?

A

Protein disulphide isomerase (PDI)

98
Q

What does the oxidised PDI have?

A

A disulphide bond in it’s active site

99
Q

How does PDI work?

A

It can transfer electrons from reduced substrate protein to that disulphide bond to generate a disulphide bond in the substrate protein, producing reduced PDI and the oxidised substrate

100
Q

What will have happened to proteins with disulphide bonds?

A

They will have passed through the ER

101
Q

What kind of proteins tend to have disulphide bonds?

A

Extracellular or secreted proteins

102
Q

What does the KDEL receptor do?

A

Forms a transmembrane link between ER-resident proteins and the COPI-coat

103
Q

How does a soluble ER resident protein differ from secreted proteins?

A

By KDEL sequence before the -COOH

104
Q

What is the KDEL sequence?

A

Lys-Asp-Glu-Leu

105
Q

What does the KDEL sequence do?

A

Bind to the KDEL receptor

106
Q

Where are soluble ER resident proteins synthesised?

A

ER lumen

107
Q

What happens to the soluble ER resident protein once it’s been synthesised?

A
  • Vesicles bud off from ER, containing the protein, and transported to cis-golgi
  • In the cis-golgi, KDEL containing proteins are recognised by specific receptors, causing it to bud off, and be returned to RER
108
Q

Why must soluble ER resident proteins be returned to ER after going to cis-golgi?

A

Don’t want it to get any further and get secreted

109
Q

How is the KDEL cycle regulated?

A

Regulated binding due to pH

110
Q

How does KDEL binding regulation due to pH work?

A

Cis-Golgi is more acidic that the ER, so under these conditions, KDEL containing proteins have a higher affinity for the receptor, enabling it to bind and then be released when it returns to the ER

111
Q

What happens if there are folding problems?

A
  • Protein may be trapped in mis-folded conformation

- Protein may be incorrectly associated with other sub-units

112
Q

What attempts to correct folding problems?

A

ER chaperone proteins

113
Q

Give 3 examples of chaperone proteins?

A
  • BiP
  • Calnexin
  • Calreticulin
114
Q

What does BiP do?

A

Binds to exposed amino acid sequences that would normally be buried in the interior of a folded protein

115
Q

What does calnexin and calreticulin do?

A

Binds to oligosaccharides on incompletely folded proteins

116
Q

Where are chaperone proteins important?

A

For quality control

117
Q

What are the functions of chaperones?

A
  • Retain unfolded proteins in the ER to prevent secretion
  • Acts as sensors to monitor the extent of protein misfolding
  • Mediate increased transcription of chaperones
  • Mediate reduction in translation
118
Q

What happens if misfolding can’t be corrected?

A

NAME?

119
Q

What are the two mechanisms by which protein misfolding can cause disease?

A
  • Mutations resulting in disposal

- Misfolding causing retention

120
Q

How can misfolding causing retention cause disease?

A
  • Gain of toxic function

- Loss of function

121
Q

What occurs in the cis-Golgi network?

A

NAME?

122
Q

What occurs in the cis cisterna of Golgi stack?

A

Removal on Man

123
Q

What occurs in the medial cisterna of Golgi stack?

A

NAME?

124
Q

What happens in the trans cisterna of the Golgi stack?

A
  • Addition of Gal

- Addition of NANA

125
Q

What happens in the trans Golgi network?

A
  • Sulfation of tyrosines and carbohydrates

- Sorting → lysosome, plasma membrane or secretory vesicle

126
Q

What do the lysosomes need to have?

A

The correct components of enzymes to carry out degradative functions

127
Q

What does delivery of lysosomal enzymes to the lysosome require?

A

A mannose-6-phosphate signal

128
Q

What happens as a lysosomal enzyme passes through the Golgi apparatus?

A

It’s recognised by enzymes, and a phosphate group is added to the hydroxyl group on carbon 6 of a mannose sugar

129
Q

What enzymes does the addition of a phosphate group to the mannose sugar on lysosomal enzymes require?

A
  • N-acetylglucosamine phosphotransferase

- A phosphodiesterase

130
Q

What does the glucosamine phosphotransferase do?

A

Recognises a signal patch (not a linear sequence)

131
Q

What does the phosphodiesterase do?

A

Removes N-acetylglucosamine, to leave phosphate in 6-position on mannose sugar

132
Q

Give the overall equation for to addition of a phosphate group to lysosomal enzymes

A

UDP-GlcNAc + lysosomal enzyme → UMP + GlcNAc + M6p-tagged lysosomal enzyme

133
Q

What is a I-cell disease?

A

A fatal inherited condition whereby there is a deficiency in N-actyl glucosamine phosphotransferase

134
Q

What happens in I-cell disease?

A

The lysosomes become bloated with undegraded material

135
Q

What does the mannose-6-phosphate receptor mediate?

A

The delivery of lysosomal enzymes from the trans-Golgi network to the lysosomes

136
Q

Where are lysosomal enzymes modified?

A

In the trans-Golgi network

137
Q

What happens when lysosomal enzymes get to the trans-Golgi network?

A

It binds to the M6P receptor

138
Q

What happens when the M6P receptor binds to lysosomal enzymes?

A

It initiates the formation of the clathrin coat, which causes the vesicles to pinch off

139
Q

What happens when the vesicles with lysosomal enzymes have pinched off?

A

It undergoes receptor-dependent transport, until it fuses with the late endosome

140
Q

What happens when the vesicle has fused with the late endosome?

A

The enzyme dissociates from the receptor at the acidic pH

141
Q

What happens to the receptor when the enzyme has dissociated?

A

It pinches off into the transport vesicle, and is recycled back to the trans golgi network

142
Q

How is a mature lysosomal hydrolase formed?

A

The phosphate group is removed from the enzyme

143
Q

What is formed once the enzyme becomes a mature lysosomal hydrolase?

A

The late endosome becomes a lysosome

144
Q

What is O-linked glycosylation?

A

Attachment of sugar to -OH group

145
Q

Where does O-linked glycosylation occur?

A

In the Golgi

146
Q

Where is the sugar attached in O-linked glycosylation?

A

To hydroxyl group of serine and threonine

147
Q

Where is O-linked glycosylation important?

A

In proteoglycans

148
Q

What are proteoglycans?

A

A component of the extracellular matrix and mucus secretions

149
Q

How may proteins be delivered to the plasma membrane?

A

Via a regulated or constitutive pathway

150
Q

What happens to proteins destined for either unregulated secretion of constituent secretion?

A

Vesicles bud off from the trans-Golgi network containing the proteins

151
Q

How do proteins for constitutive secretion enter the extracellular space?

A

Unregulated membrane fusion

152
Q

Other than proteins for constitutive secretion, what else uses the same vesicles?

A

Newly synthesised plasma membrane proteins and lipids

153
Q

What happens to proteins for regulated membrane fusion?

A

They bud off into secretory vesicles, and remain there until a signal such as a hormone or neurotransmitter are released into the intracellular signalling pathway. The proteins are then released into the extracellular space by regulated membrane fusion

154
Q

What is the most abundant protein in the body?

A

Collagen

155
Q

Where is collagen found?

A
  • Tendons
  • Ligaments
  • Cartilage
  • Bone
  • Loose connective tissue
156
Q

What is the purpose of collagen in loose connective tissue?

A

It provides structure to internal organs

157
Q

What produces collagen?

A

By fibroblasts in connective tissue

158
Q

What is the basic unit of collagen fibres?

A

Tropocollagen

159
Q

Describe the shape of tropocollagen?

A

300nm rod-shaped protein

160
Q

What does tropocollagen consist of?

A

3 polypeptides (α-chains), each ~1000aa long

161
Q

What is the important feature of the primary structure of collagen?

A

There is a glycine at every 3rd position along each α-chian

162
Q

Where is the Gly-X-Y repeat important?

A

In assembly of collagen polypeptide

163
Q

What shape to the α-chains of collagen form?

A

Triple helix

164
Q

What does the glycine at every 3rd position allow in collagen?

A

The 3 α-chains the assemble together into the triple helix, as glycine is a very small amino acids

165
Q

How is the collagen triple helix stabilised?

A

Hydrogen bonding between different α-chains

166
Q

What are the features of tropocollagen’s structure?

A
  • Non-extensible
  • Non-compressible
  • High tensile strength
167
Q

What does tropocollagen have at the X and some Y positions?

A

Mostly proline or hydroxyproline

168
Q

What is the result of proline being in the tropocollagen structure?

A

The secondary structure can’t be an α-helix, as proline as a helix breaker

169
Q

What do different α-chains assemble to make up?

A

Different collagens in different parts of the body

170
Q

What does different combinations of α-chains produce?

A

Collagens with different functions

171
Q

What appearance does collagen have?

A

Regular, repeating grooves

172
Q

What produces the regular repeating grooves in collagen?

A

The assembly of tropocollagen within collagen

173
Q

How is collagen synthesised and modified in the ER?

A
  • Chain synthesised and enters lumen of ER
  • Signal peptide cleaved as it enters the ER lumen
  • Selected proline and lysine residues are hydroxylated
  • N-linked oligosaccharides added
  • Addition of galactose to hydroxylysine residues
  • Chain alignment
  • Formation of triple-helical procollagen from C- to N- terminus
  • Completion of O-linked oligosaccharide chains by addition of glucose
  • Procollagen buds off into transport vesicle
  • Vesicle fuses with plasma membrane
  • Protein released into extracellular space, N and C terminal propeptides removed
  • Lateral association of collagen molecules followed by covalent cross-linking
  • Aggregation of fibrils to make collagen fibre
174
Q

What happens when the signal peptide of tropocollagen is cleaved in the ER?

A

Propro α-chains are converted into pro α-chains

175
Q

What catalyses the hydroxylation of proline and lysine residues?

A

Prolyl hydroxylase

176
Q

What does prolyl hydroxylase require for function?

A
  • Vit C, as cofactor

- Fe 2+

177
Q

What is prolyl hydroxylase associated with?

A

PDI in ER

178
Q

What does prolyl hydroxylase allow?

A

H-bonding to stabilise triple helix

179
Q

How does prolyl hydroxylase allow increased H bonding?

A

Adding extra hydroxyl groups on proline that are able to form H bonds

180
Q

What is scurvy due to?

A

Weak tropocollagen triple helices

181
Q

What is galactose added to hydroxylysine residues involved in?

A

Interchain interactions

182
Q

Where is chain alignment stabilised?

A

At C terminal domain

183
Q

How is the chain alignment stabilised?

A

By formation of disulfide bonds

184
Q

How much of the procollagen doesn’t form the triple helix?

A
  • 150 N-terminal amino acids

- 250 C-terminal amino acids

185
Q

What are the extra N- and C- terminal amino acids that don’t form the triple helix important for?

A

Assembly of the tropocollagen unit

186
Q

What happens when the vesicle containing procollagen fuses with the plasma membrane?

A

It undergoes exocytosis

187
Q

How is procollagen converted into tropocollagen?

A

By action of procollagen peptidases

188
Q

What will happen when the N and C terminals of procollagen are removed?

A

Tropocollagen will be able to assemble with other units

189
Q

What is the purpose of covalent cross-linking of tropocollagen molecules?

A

For stability

190
Q

Why is it important that aggregation of tropocollagen fibrils is tightly regulated?

A

Because if cleavage of N and C terminal peptides too early, could assemble in cell

191
Q

How are tropocollagen’s cross linked?

A

Two lysine residues in different tropocollagen units are covalently linked

192
Q

How are two lysine residues covalently linked?

A

By action of lysyl oxidase and addition of oxygen, which forms two aldehyde derivatives, which spontaneously link to form a aldol cross link

193
Q

Where is lysyl oxidase found?

A

Extracellular

194
Q

Why is it important that lysyl oxidase is extracellular?

A

Prevents covalent cross linking of collagens within the cell

195
Q

What does lysyl oxidase require for activity?

A
  • Vitamin B6

- Cu 2+

196
Q

What causes Ehlers-Danlos syndrome?

A

A mutation in collagen type V or a lysyl oxidase deficiency

197
Q

How is insulin secreted?

A

As proinsulin

198
Q

How many polypeptides is proinsulin made up of?

A

1

199
Q

What must happen to proinsulin in order for it to fold properly?

A

Form 3 disulphide bonds- 2 interchain, one internal

200
Q

Where does the formation of disulphide bonds in proinsulin occur?

A

In the ER

201
Q

What must happen for proinsulin to become activated?

A

The connecting C peptide is removed, leaving complete 2 chain insulin molecule

202
Q

Where does proinsulin activation occur?

A

Post-Golgi

203
Q

What enzymes does proteolytic processing of insulin require?

A
  • PC3 endoprotease
  • PC2 endoprotease
  • Carboxypeptidase
204
Q

What can proteolytic processing yield?

A

Different products

205
Q

How can proteolytic processing yield different products?

A

Because there are different amounts of processing enzymes in different cell locations

206
Q

Why is proteolytic processing so common in secretory pathways?

A
  • Can give rise to very small products that would be too short to enter ER via co-translational mechanism
  • Some secreted proteins would be destructive if activated inside the cell
  • Multiple bioactive products can be produced from some polypeptides
  • Avoids activation of insulin receptor in the secretory pathway

Z OLD Molecules, Genes and Disease (14 decks)

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