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MGD > Protein Processing > Flashcards

Protein Processing Flashcards

1
Q

In which 2 places can ribosomes be?

A

attached to RER or in cytosol

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2
Q

Where would the ribosome be if the protein being synthesised was destined for secretion or the membrane?

A

attached to RER

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3
Q

Where would the ribosome be if the protein being synthesised is destined for the cytosol or organelles?

A

In the cytosol

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4
Q

Where on the protein is the signal if it is destined to go to the ER?

A

N terminus

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5
Q

If destined for the ER, is the protein folded during transfer and what are the specialised proteins required?

A

No - it is unfolded during transfer

SRP - signal recognition protein
SRP receptor

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6
Q

Is the signal cleaved if destined for the ER?

A

Yes - by signal peptidase

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7
Q

Does protein transfer to the ER require energy?

A

Yes - GTP

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8
Q

What do we call the signal if the protein is destined for the nucleus?

A

NLS - nuclear localising signal

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9
Q

Where is the NLS found?

A

On the surface of the folded protein

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10
Q

What are the 2 important proteins for processing into the nucleus and what do they do?

A

Importin - recognises NLS and mediates transport

RanGTP - displaces importin in the nucleus

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11
Q

Is the signal cleaved in nuclear transport?

A

No - the signal is retained because it is needed in cell division

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12
Q

What kind of signal is required for mitochondrial transport and where is it located?

A

Amphipathic signal

N terminus

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13
Q

Is the protein folded during transport to the mitochondria?

A

No

It is held partially unfolded by a chaperone protein (MSF)

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14
Q

What does MSF stand for?

A

Mitochondrial-import stimulating factor

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15
Q

What specialist proteins are required for transport into the mitochondria?

A

MSF: chaperone protein
TOM: transport channel on outer membrane
TIM: transport channel on inner membrane

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16
Q

Is the signal cleaved during mitochondrial transfer?

A

Yes

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17
Q

Is energy required for mitochondrial transfer?

A

Yes - ATP

18
Q

What is the signal for transport to lysosomes?

A

mannose-6-phosphate

Added post-translation

19
Q

Is the protein folded during transfer to lysosomes?

A

Yes - it is delivered in a vesicle

20
Q

Where is the M-6-P receptor?

A

Trans-Golgi

21
Q

Is the signal removed after transport the lysosomes?

A

Yes - the phosphate is cleaved by phosphatase

22
Q

Is energy required for transport to lysosomes?

A

Yes - ATP

23
Q

What and where is the signal for retention in the ER?

A

KDEL signal

C terminus

24
Q

What is constitutive secretion?

A

When something is being secreted all the time. It does not rely on stimulation.

25
Q

Is the protein folded during retention in the ER?

A

Yes - it is transported via vesicle

26
Q

What and where is the receptor for the KDEL signal?

A

KDEL receptor

Cis-Golgi

27
Q

Is the signal cleaved for retention in the ER?

A

No - is required to keep the process going

28
Q

Is energy required for retention in the ER?

A

No

Except a very small amount is required for the budding off of vesicles

29
Q

How could someone have pyruvate dehydrogenase deficiency due to a fault in the protein processing?

A

If there is a mutation in the mitochondrial targeting sequence on pyruvate dehydrogenase then it cannot enter the mitochondria.

30
Q

What is Swyer Syndrome?

A

The loss or mutation of NLS in the sex determining region of the Y protein.
You would be outwardly female as there is no testis differentiation.

31
Q

What is the SHOX transcription factor required for?

A

Skeletal development

32
Q

What are the functions of the ER?

A 
insertion of proteins into membranes
specific proteolytic cleavage
glycosylation
formation of disulfide bonds
folding of proteins
assembly of some multi subunit proteins
hydroxylation of selected Lys and Pro residues
33
Q

What is glycosylation important for?

A

correct folding, stability and interaction with other molecules

34
Q

How does N-linked glycosylation work?

A

Sugars are added to an asparagine side chain.

35
Q

What does the enzyme protein disulfide Isomerase do?

A

Forms disulfide bonds in the ER

36
Q

How does O-linked glycosylation work?

A

Attachment of sugar to the -OH group of serine or threonine in the Golgi.

37
Q

What is tropocollagen?

A

the basic unit of collagen

3 polypeptide alpha chains in a triple helix

38
Q

Which 2 enzymes are important in collagen synthesis and what do they do?

A

Prolyl hydroxylase - hydroxylation of selected Pro and Lys residues

Lysyl oxidase - allows covalent cross-linking of collagen molecules to form fibres

39
Q

Which enzyme requires vitamin C?

A

Prolyl hydroxylase

40
Q

What is the simple sequence of events for collagen synthesis?

A
  1. Enters RER
  2. Cleavage of signal
  3. Hydroxylation
  4. N linked glycosylation
  5. Addition of galactose
  6. Disulfide bond formation
  7. Triple helix formation
  8. Addition of glucose
  9. Vesicle to exocytosis
  10. Terminal propeptide removal
  11. Covalent cross-linking
  12. Aggregation of fibrils to fibres
41
Q

What are the 2 causes of Ehlers-Danos Syndrome? (Stretchy skin)

A

mutation in type III or V collagen

Lysyl oxidase deficiency

MGD (13 decks)

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