Post-Translational Protein Modification

Question 1

Define the properties of a protein

Answer 1

Fundamental cellular component
polymeric
Macromolecule
Polypeptide

Question 2

How many amino acids make up a protein

Answer 2

> 40

Question 3

What is a polypeptide

Answer 3

Many amino acid monomer linked together by peptide bonds.

Question 4

What are the two types of tertiary folding

Answer 4

Fibrous

Globular

Question 5

Define a primary structure protein

Answer 5

Amino acid sequence

Question 6

Define secondary Structure

Answer 6

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

Question 7

Define tertiary structure

Answer 7

3D folding of a single polypeptide chain

Question 8

Define quaternary structure

Answer 8

Assembly of multiple proteins into a complex

Question 9

How does sickle cell disease occur

Answer 9

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

Question 10

What bonds are held in a tertiary structure

Answer 10

Hydrogen bonding
- Between the R groups

Ionic bonds
Between Co2 and NH3 of R groups

Disulphide brides
- Between cystine and SH groups

Hydrophobic interactions

Question 11

What are proproteins

Answer 11

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

Question 12

How are proproteins used to get insulin

Answer 12

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.

Question 13

What steps are involved in post translational modifications.

Answer 13

Processing

Covalent modification

Question 14

What is the significance of post-transaltional protein modifications

Answer 14

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.

Question 15

Define proteolytic cleavage

Answer 15

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

Question 16

Is proteolytic cleavage reversible

Answer 16

no

Question 17

Define proline isomerisation

Answer 17

The change in proline residue spatial conformation

e.g cis and trans

Question 18

What additional small functional groups does Post translational modification occur.

Answer 18

Phosphorylation
Acetylation
Methylation
Hydroxylation

Question 19

Define Protein phosphorylation

Answer 19

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

Question 20

Is protein phosphorylation reversible

Answer 20

Yes it can be de-phosphorylated

Question 21

Which biological processes can reverse protein phosphorylation do

Answer 21

Pyruvate dehydrogenase

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

Question 22

What do cyclin dependent manses phosphorylate

Answer 22

Serine

Threonine

Question 23

When do CDKs only work

Answer 23

When they are attached to a cyclin

Question 24

What can influence the behaviour of CdK

Answer 24

The type of cyclin used

Question 25

What drives the cell cycle

Answer 25

Cyclin concentration

Question 26

Which amino acid is most commonly phosphorylated

Answer 26

Serine

Question 27

What does tyrosine phosphorylation lead to

Answer 27

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

Question 28

What are the ways you can detect phosphorylated proteins by

Answer 28

Phospho-specifc antibodies 2-Dimension phosphopeptide mapping with 32P

Question 29

What is protein acetylation

Answer 29

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

Question 30

In protein de/acetylation what is the reaction catalysed by

Answer 30

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

Question 31

What are the most characterised targets of protein acetylation

Answer 31

Histones

Question 32

Define protein methylation

Answer 32

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

Question 33

What is the reaction catalysed by in protein methylation

Answer 33

protein methyltransferase

Question 34

What are the 2 major amnio acids methylated

Answer 34

Arginine and Lysine

Question 35

How does PTMs change the chemical nature of amino acids

Answer 35

citrullination or deimiantion of arginine converting it to citrulline

Question 36

What large functional groups are involved in PTMs

Answer 36

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

Question 37

Define Protein glycoslation

Answer 37

Adding mono or poly saccharides to a protein.

Question 38

What is N/O linked glycoslation

Answer 38

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.

Question 39

How is N linked oliosaccahrides processed

Answer 39

Removal of three glucose residues in the ER | Mannose residues removed and other sugars added in the golf apparatus

Question 40

What is ubiquitin

Answer 40

Small protein only containing 76 amino acids

Question 41

What is ubquitin attached to in protein

Answer 41

Lysine

Question 42

What does the attachment of mono ubiquitin do

Answer 42

Change protein structure

Question 43

What does the attachment of polyubiqutin do

Answer 43

Marks for protein degradation in a proteasome.

Question 44

What are the three enzymes needed for ubiquination

Answer 44

Ubiquitin activating enzymes Ubiquitin conjugating Ubiquitin ligase

Question 45

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

Answer 45

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

Question 46

What is lipidation

Answer 46

Method to target proteins to membranes in organelles

Question 47

What are the 4 types of lipidation

Answer 47

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