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Intergrated Medical Sciences > Post-Translational Protein Modification > Flashcards

Post-Translational Protein Modification Flashcards

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USMLE® Step 1 flashcards
1
Q

Define the properties of a protein

A

Fundamental cellular component
polymeric
Macromolecule
Polypeptide

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2
Q

How many amino acids make up a protein

A

> 40

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3
Q

What is a polypeptide

A

Many amino acid monomer linked together by peptide bonds.

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4
Q

What are the two types of tertiary folding

A

Fibrous

Globular

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5
Q

Define a primary structure protein

A

Amino acid sequence

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6
Q

Define secondary Structure

A

Interactions between adjacent amino acids such a alpha helices beta pleated sheets and random coils.

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7
Q

Define tertiary structure

A

3D folding of a single polypeptide chain

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8
Q

Define quaternary structure

A

Assembly of multiple proteins into a complex

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9
Q

How does sickle cell disease occur

A

Single mutation in beta globing gene where T to A in the primary sequence. GLU to VAL

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10
Q

What bonds are held in a tertiary structure

A

Hydrogen bonding
- Between the R groups

Ionic bonds
Between Co2 and NH3 of R groups

Disulphide brides
- Between cystine and SH groups

Hydrophobic interactions

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11
Q

What are proproteins

A

Inactive peptides or proteins that need post translational modifications to activate them.

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12
Q

How are proproteins used to get insulin

A

Ribosomes feed the growing amino acid chain and directly into the ER where the signal peptide is immediately cleaved off by a signal peptidase to yield proinsulin.

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13
Q

What steps are involved in post translational modifications.

A

Processing

Covalent modification

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14
Q

What is the significance of post-transaltional protein modifications

A

Covalent modifications allow the extension of structural repertoire of proteins. And the changes in chemical structure of protein leads to the change in spatial structure and biological activity.

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15
Q

Define proteolytic cleavage

A

cleavage of a protein at a peptide bond. One or several amino acids could be removed from N terminus of protein

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16
Q

Is proteolytic cleavage reversible

A

no

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17
Q

Define proline isomerisation

A

The change in proline residue spatial conformation

e.g cis and trans

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18
Q

What additional small functional groups does Post translational modification occur.

A

Phosphorylation
Acetylation
Methylation
Hydroxylation

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19
Q

Define Protein phosphorylation

A

Phosphate donated by ATP which is transferred from an acceptor protein which is catalysed by protein kinase.

20
Q

Is protein phosphorylation reversible

A

Yes it can be de-phosphorylated

21
Q

Which biological processes can reverse protein phosphorylation do

A

Pyruvate dehydrogenase

- by protein kinase activated by high NADH and NAD and inhibited by pyruvate.

22
Q

What do cyclin dependent manses phosphorylate

A

Serine

Threonine

23
Q

When do CDKs only work

A

When they are attached to a cyclin

24
Q

What can influence the behaviour of CdK

A

The type of cyclin used

25
Q

What drives the cell cycle

A

Cyclin concentration

26
Q

Which amino acid is most commonly phosphorylated

A

Serine

27
Q

What does tyrosine phosphorylation lead to

A

Leads to binding of specific proteins that promote protein to protein interactions

28
Q

What are the ways you can detect phosphorylated proteins by

A

Phospho-specifc antibodies

2-Dimension phosphopeptide mapping with 32P

29
Q

What is protein acetylation

A

acetyl group is donated by acetyl coenzyme A and is transferred to an acceptor amino acid lysine in protein.

30
Q

In protein de/acetylation what is the reaction catalysed by

A

protein acetylation
Catalysed by Protein AcetylTransferase (PAT). Process of a protein deacetylation is catalyzed by a Protein DeACetylase (PDAC).

31
Q

What are the most characterised targets of protein acetylation

A

Histones

32
Q

Define protein methylation

A

Process where methyl group donated by s-adenosylmethionine is transferred to an acceptor protein.

33
Q

What is the reaction catalysed by in protein methylation

A

protein methyltransferase

34
Q

What are the 2 major amnio acids methylated

A

Arginine and Lysine

35
Q

How does PTMs change the chemical nature of amino acids

A

citrullination or deimiantion of arginine converting it to citrulline

36
Q

What large functional groups are involved in PTMs

A

Glycoslation
Addition of peptides and proteins
Additon of fatty acids and lipid residues

37
Q

Define Protein glycoslation

A

Adding mono or poly saccharides to a protein.

38
Q

What is N/O linked glycoslation

A

N linked
polysaccharide is added to a 14 sugar unit to asparagine residue of the newly synthesised polypeptide in the ER

O linked
Sugar added one at a time in Golgi or in the cytoplasm the sugar is usually added to hydroxyl group of serine or threonine.

39
Q

How is N linked oliosaccahrides processed

A

Removal of three glucose residues in the ER

Mannose residues removed and other sugars added in the golf apparatus

40
Q

What is ubiquitin

A

Small protein only containing 76 amino acids

41
Q

What is ubquitin attached to in protein

A

Lysine

42
Q

What does the attachment of mono ubiquitin do

A

Change protein structure

43
Q

What does the attachment of polyubiqutin do

A

Marks for protein degradation in a proteasome.

44
Q

What are the three enzymes needed for ubiquination

A

Ubiquitin activating enzymes
Ubiquitin conjugating
Ubiquitin ligase

45
Q

What are some of the biological processes of protein polyubiquitination and proteasomal degradation

A

Removal of damaged and misfolded proteins
Control the lidepan of different proteins
Control multiple cellular processes

46
Q

What is lipidation

A

Method to target proteins to membranes in organelles

47
Q

What are the 4 types of lipidation

A

C- terminal glycosyl phosphatidylinostiol
N- terminal myristoylation
S- myristoylation
S- prenylation

Intergrated Medical Sciences (38 decks)

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