W2- Lecture 10- Post-translational Modifications Of Proteins Flashcards
Over what no of amino acids can a poly pep time fold into a defined shape ?
40 AA
Primary secondary’s and tertiary structure of proteins
1- sequence of aa
2- interaction between aa e.g alpha helixes or beta sheets , loops and coils
3- 3D shape
4 - more then one protein = complex
What direction / terminus do we read
AA form/to ?
N terminus to the C terminus
What mutation causes sickle cell disease ?
mutation in hba haemoglobin/ beta globin gene sunbsitation from T to A
Glu to val
Side chain changes which causes impact
Where can we find the ionic bonds / electrostatic attraction ?
In the r group between
CO2- and NH3+
Where can we find the disulfide bridges ?
Between cysteine and SH Groups
Cys-S-S-Cys
What are proproteins?
Inactive proteins that need activation before use
Where is the preproinsulin fed from / into ?
Ribosomes feed into ER
Name the three steps of post translational modification of proinsulin
+ where
All in ER 1- Cleavage and removal of signal peptides 2-Oxidation of SH groups to SS (disulfide bridge formation ) 3- Cleavage and removal of the C chain
Why is post translational mod of proteins important ?
- to allow proteins to have a different spacial arrangement / biological activity
- allows regulation of proteins
- Increases protein diversity
Name different PTM
Cleavage
isomerism
Addition of Small molecules e.g phosporylation
Describe protein phosphorylation
Phosphate group donated by ATP
Catalysed by protein kinase
What enzyme catalysed the back reaction of phosphorylation of a protein ?
Phosphatase
Describe how pyruvate dehydrogenase is regulated by phosphorylation/ de phosphorylation
phosphorylation/ de phosphorylation is regulated by protein kinase
Activated by high NADH and AcetylCoA
but inhibited by pyruvate
Explain how EGF receptor binds with ligand and how phosphorylation takes place + impact
- when binds to ligand
- forms firmer
- phosphorylation each other
- activates of genes- can lead to excess cell growth
What is the cell cycle dependant on ?
Cyclin and cyclin dependant kinases
How do Cyclin and cyclin dependant kinases act to promote the cell cycle
CDK and cyclins only work when boundtogether
- CDKs phosphorylate serine is threonine
- promotes cycle from moving to the next step in the cycle
- type of cyclin and concentration drive cell cycle
What are the two most phosphorylated AA?
Serine
Threonine (often associated with each other)
What does tyrosine phosphorylation cause ?
Activation off signalling networks but activator gets protein protein interactions
Detecting phosphorylated proteins
Phospho-specific antibodies
2d electrophoresis + western blotting
describe protein acetylation
Acetyl group is donated by acetyl Coenzyme A to a lysine
Catalysed by protein acetyltransferase (PAT)
Describe the deacetylation of a protein
Catalysed by protein DeACetylase (PDAC)
Where an acetyl group is removed from the amino acid lysine within a protein
Where is the primary target for acetylation
Histones
Describe protein methylation
Methyl group donated by S-adenosylmethionie
Catalysed by protein methyl transferase
Majorly arginine and lysine
Not all reversible
