Post-Translational Protein Modification Flashcards
Define the properties of a protein
Fundamental cellular component
polymeric
Macromolecule
Polypeptide
How many amino acids make up a protein
> 40
What is a polypeptide
Many amino acid monomer linked together by peptide bonds.
What are the two types of tertiary folding
Fibrous
Globular
Define a primary structure protein
Amino acid sequence
Define secondary Structure
Interactions between adjacent amino acids such a alpha helices beta pleated sheets and random coils.
Define tertiary structure
3D folding of a single polypeptide chain
Define quaternary structure
Assembly of multiple proteins into a complex
How does sickle cell disease occur
Single mutation in beta globing gene where T to A in the primary sequence. GLU to VAL
What bonds are held in a tertiary structure
Hydrogen bonding
- Between the R groups
Ionic bonds
Between Co2 and NH3 of R groups
Disulphide brides
- Between cystine and SH groups
Hydrophobic interactions
What are proproteins
Inactive peptides or proteins that need post translational modifications to activate them.
How are proproteins used to get insulin
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.
What steps are involved in post translational modifications.
Processing
Covalent modification
What is the significance of post-transaltional protein modifications
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.
Define proteolytic cleavage
cleavage of a protein at a peptide bond. One or several amino acids could be removed from N terminus of protein
Is proteolytic cleavage reversible
no
Define proline isomerisation
The change in proline residue spatial conformation
e.g cis and trans
What additional small functional groups does Post translational modification occur.
Phosphorylation
Acetylation
Methylation
Hydroxylation
Define Protein phosphorylation
Phosphate donated by ATP which is transferred from an acceptor protein which is catalysed by protein kinase.
Is protein phosphorylation reversible
Yes it can be de-phosphorylated
Which biological processes can reverse protein phosphorylation do
Pyruvate dehydrogenase
- by protein kinase activated by high NADH and NAD and inhibited by pyruvate.
What do cyclin dependent manses phosphorylate
Serine
Threonine
When do CDKs only work
When they are attached to a cyclin
What can influence the behaviour of CdK
The type of cyclin used
What drives the cell cycle
Cyclin concentration
Which amino acid is most commonly phosphorylated
Serine
What does tyrosine phosphorylation lead to
Leads to binding of specific proteins that promote protein to protein interactions
What are the ways you can detect phosphorylated proteins by
Phospho-specifc antibodies
2-Dimension phosphopeptide mapping with 32P
What is protein acetylation
acetyl group is donated by acetyl coenzyme A and is transferred to an acceptor amino acid lysine in protein.
In protein de/acetylation what is the reaction catalysed by
protein acetylation
Catalysed by Protein AcetylTransferase (PAT). Process of a protein deacetylation is catalyzed by a Protein DeACetylase (PDAC).
What are the most characterised targets of protein acetylation
Histones
Define protein methylation
Process where methyl group donated by s-adenosylmethionine is transferred to an acceptor protein.
What is the reaction catalysed by in protein methylation
protein methyltransferase
What are the 2 major amnio acids methylated
Arginine and Lysine
How does PTMs change the chemical nature of amino acids
citrullination or deimiantion of arginine converting it to citrulline
What large functional groups are involved in PTMs
Glycoslation
Addition of peptides and proteins
Additon of fatty acids and lipid residues
Define Protein glycoslation
Adding mono or poly saccharides to a protein.
What is N/O linked glycoslation
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.
How is N linked oliosaccahrides processed
Removal of three glucose residues in the ER
Mannose residues removed and other sugars added in the golf apparatus
What is ubiquitin
Small protein only containing 76 amino acids
What is ubquitin attached to in protein
Lysine
What does the attachment of mono ubiquitin do
Change protein structure
What does the attachment of polyubiqutin do
Marks for protein degradation in a proteasome.
What are the three enzymes needed for ubiquination
Ubiquitin activating enzymes
Ubiquitin conjugating
Ubiquitin ligase
What are some of the biological processes of protein polyubiquitination and proteasomal degradation
Removal of damaged and misfolded proteins
Control the lidepan of different proteins
Control multiple cellular processes
What is lipidation
Method to target proteins to membranes in organelles
What are the 4 types of lipidation
C- terminal glycosyl phosphatidylinostiol
N- terminal myristoylation
S- myristoylation
S- prenylation
