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IMS > POST-TRANSLATIONAL PROTEIN MODIFICATION > Flashcards

POST-TRANSLATIONAL PROTEIN MODIFICATION Flashcards

1
Q

what is the lowest and most state shape for proteins?

A

their final 3D conformation

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2
Q

what develops before the tertiary structure?

A

Small regions of relatively stable secondary structure

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3
Q

what does tertiary folding result in?

A

fibrous or globular protein

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4
Q

what are proproteins?

A

inactive peptides or proteins

that need post-translational modifications to activate them

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5
Q

give an example of pro-forms of protein

A

production of insulin

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6
Q

how is insulin produced?

A

Ribosomes feed the growing AA chain (preproinsulin) directly into the ER where the signal peptide is immediately cleaved off by a signal peptidase to yield proinsulin. This is later processed further to mature and active insulin.

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7
Q

what is the 1st Post-translation modification event?

A

Cleavage and removal of signal peptide by signal peptidase in ER.

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8
Q

what is the 2nd Post-translation modification event?

A

Oxidation of -SH groups to -S-S- (disulphide bridges) in ER. This cross-links specific regions via the -S-S- covalent bond.

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9
Q

what is the 3rd Post-translation modification event?

A

Cleavage and removal of the C chain in ER.

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10
Q

what can Post-translational modifications involve?

A

processing

covalent modification

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11
Q

what is processing?

A

proteolytic cleavage to an active form

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12
Q

what is covalent modification?

A

the chemical modification of a protein after its translation

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13
Q

what happens during translation?

A

a polypeptide chain containing up to 20 genetically encoded AA is synthesized

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14
Q

what does covalent modification allow?

A

allow to significantly extend the structural repertoire of proteins

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15
Q

what do the changes in chemical structure of a protein lead to?

A

leads to the change in its spatial structure and biological activity

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16
Q

what does PTM’s of proteins being reversible allow?

A

allows rapid dynamic regulation of a protein activity by controlling the balance of reversible PTMs

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17
Q

what does the control of PTMs of proteins allow?

A

allow the control of their activity. This principle is widely used in nature to regulate numerous biological processes

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18
Q

what biological processes are controlled by PTM?

A

metabolism, cellular signaling, gene transcription

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19
Q

what is PTMs and de-modifications of proteins catalysed by?

A

by enzymes that are involved in the regulation of their target protein activity

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20
Q

what are PTM’s a key mechanism for?

A

to increase proteomic diversity

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21
Q

where does proteolytic cleavage occur?

A

at a peptide bond

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22
Q

wat occurs during proteolytic cleavage?

A

One or several AA could be removed from N-terminus of a protein, or protein peptide bond could be cleaved in the internal part of the protein

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23
Q

what is proline isomerisation?

A

the change in proline residue spatial conformation (transition between cis- and trans- conformations of peptide bonds involving proline)

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24
Q

what can proline isomerisation affect?

A

Can seriously affect protein structure adopted

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25
Q

what do PTMs involve the addition of?

A

small functional groups

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26
Q

give examples of functional groups added to PTMs

A

Phosphorylation
Acetylation
Methylation
Hydroxylation

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27
Q

what is protein phosphorylation?

A

process in which phosphate group, donated by ATP, is transferred to an acceptor protein

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28
Q

what catalyses the protein phosphorylation reaction?

A

protein kinase

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29
Q

is protein phosphorylation reversible or irreversible?

A

reversible

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30
Q

what is protein de-phosphorylation catalysed by?

A

protein phosphatase

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31
Q

what is pyruvate dehydrogenase regulated by?

A

by phosphorylation/ dephosphorylation by a protein kinase

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32
Q

what is protein kinase activated and inhibited by for pyruvate dehydrogenase?

A

activated by high [NADH]:[NAD+] and [acetylCoA]: [CoA], but inhibited by pyruvate

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33
Q

what is the cell cycle controlled by?

A

cyclins and their cyclin dependent kinases CDKs

34
Q

what is the most commonly phosphorylated AA?

A

Serine followed by threonine

35
Q

what does tyrosine phosphorylation lead to?

A

binding of specific proteins that promote protein:protein interactions as part of the signaling networks

36
Q

how do you detect phosphorylated proteins?

A

Phospho-specific antibodies
2-Dimension Phosphopeptide
mapping with 32 P

37
Q

what is protein acetylation?

A

process in which acetyl group, donated by acetyl Coenzyme A, is transferred to an acceptor amino acid, lysine, in protein

38
Q

what is protein acetylation catalysed by?

A

by a Protein AcetylTransferase (PAT)

39
Q

what is protein deacetylation catalysed by?

A

Protein DeACetylase (PDAC)

40
Q

what is the most characterized targets of protein acetylation?

A

histones

41
Q

what are the histone PATs and PDACs called?

A

histone acetyltransferases (HATs) and histone deacetylases (HDACs)

42
Q

what does the reversible histone acetylation control?

A

gene transcription

43
Q

what is protein methylation?

A

process in which methyl group, donated by S-adenosylmethionine, is transferred to an acceptor protein

44
Q

what is protein methylation catalysed by?

A

protein methyltransferase

45
Q

what is protein demethylation catalysed by?

A

protein demethylase

46
Q

what are the 2 major amino acids methylated?

A

Arginine and Lysine

47
Q

give an example of protein methylation

A

N- methylation of lysine and arginine side chains of histones involved in gene regulation

48
Q

what is the histone code hypothesis?

A

multiple histone modifications, acting in a combinatorial or sequential manner on one/mulitple histone N-terminal tails specify unique downstream functions

49
Q

what is citrullination?

A

deimination of arginine converting it to citrulline

50
Q

what does the immune system do to citrullinated proteins?

A

attacks citrullinated proteins, and is implicated as a cause in auto-immune and arithritis diseases

51
Q

what is glycosylation?

A

addition of mono- and oligo- saccharides

52
Q

what large FG can be added to PTMs?

A

addition of other peptides or proteins (mono- and poly ubiquitination, SUMOylation)
addition of fatty acid and lipid residues

53
Q

what is protein glycosylation?

A

process of adding mono- or poly- saccharides to a protein

54
Q

what are glycoproteins?

A

Glycosylated proteins

55
Q

what does protein glycosylation have an effect on?

A

on protein conformation, distribution, stability and activity

56
Q

what biological functions does glycosylation have an effect on?

A

control of protein stability, trafficking and recognition

57
Q

what are major structural components of many cell surface and secreted proteins?

A

Carbohydrates in the form of aspargine-linked (N-linked) or serine/threonine-linked (O-linked) oligosaccharides

58
Q

where does N-linked and O-linked glycosylation take place?

A

in the ER

and Golgi apparatus

59
Q

what is N-linked glycosylation?

A

Polysaccharide is added as a 14

sugar unit to asparagine residue of the newly synthesised polypeptide in the ER.

60
Q

what is O-linked glycosylation?

A

Sugar added one in a time in Golgi, or in cytoplasm. The sugar is added usually to hydroxyl- group of serine or threonine. In some proteins hydroxy-
lysine or hydroxyproline are glycosylated

61
Q

what proteins are in the golgi?

A

secreted proteins

62
Q

what proteins are in cytoplasm?

A

cellular proteins

63
Q

give examples of types of glycosylation

A 
N-glycosylation
O-glycosylation
Glypiation 
C-glycosylation 
Phosphoglycosylation
64
Q

how can glycosidic bonds be categorised into groups?

A

based on the nature of the sugar–peptide bond and the oligosaccharide attached

65
Q

what is ubiquitin?

A

small protein containing 76 a.a.

66
Q

what is the last glycine in ubiquitin attached to?

A

to lysine in proteins

67
Q

what does the Attachment of mono-ubiquitin to a protein do?

A

plays multiple biological functions by changing the protein structure

68
Q

what is polyubiquitination?

A

Attachement of polyubiquitin chain

69
Q

what does polyubiquitination do?

A

to a protein marks the protein for degradation in a proteasome

70
Q

what 3 types of enzymes are requires for ubiquitination?

A

ubiquitin- activating enzymes, ubiquitin conjugating and ubiquitin ligase enzymes (E1, E2 and E3 respectively)

71
Q

what remove ubiquitin from proteins?

A

Deubiquitinating enzymes (DUBs)

72
Q

what are proteasome?

A

large protein complexes inside all eukaryotes, arches and some bacteria

73
Q

what is the function of proteasomes?

A

to degrade and unneeded or damaged proteins

74
Q

what are the biological functions of the protein polyubiquitination and proteasomal degradation?

A

Removal of damaged/ mis-folded proteins
Control the lifespan of different proteins
Control the multiple cellular processes

75
Q

how can you control cellular processes?

A

by regulating the availability of key regulatory proteins in these processes

76
Q

what does ubiquitination control?

A

neuronal excitability and synaptic transmission

77
Q

what is lipidation?

A

a method to traget proteins to membranes in organelles, vesicles and the plasma membrane

78
Q

what are the 4 types of lipidation?

A

C-terminal glycosyl phosphatidylinositol (GPI) anchor
N-terminal myristoylation
S-myristoylation
S-prenylation

79
Q

what does each modification of lipidation allow?

A

gives proteins distinct membrane affinities and increase the hydrophobicity of a protein

80
Q

are the different types of lipidation mutually exclusive?

A

they’re not mutually exclusive, in that 2 or more lipids can be attached to a given protein

81
Q

why are defects in protein post-traslational modifications and cell signaling important?

A

they are crucial in pathobiology of numerous diseases

82
Q

what are enzymes controlling PTMs often used as?

A

as therapeutic targets

IMS (52 decks)

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