Post translational modification Flashcards
What does Tertiary Folding result in?
Fibrous or Globular Proteins
What are Pro Proteins?
Inactive peptides or Proteins that need PTM to activate them
During Insulin Production, what modification takes place during PTM?
- Cleavage and Removal of signal peptide by signal peptidase in ER
- Oxidation of -SH groups to SS ( disulphide bridges) in ER
- Cleavage and Removal of C chain in ER
What 2 main types can PTM divide into?
- Processing ( Proteolytic Cleavage)
2. Covalent Modification ( Chemical post translation)
During Translation, what Covalent modifications would take place to a 20AA peptide that is synthesized?
Chemical process would change;
a) Spatial structure
b) Biological activity
Some PTM Proteins are Reversible, What does this result in?
Rapid Dynamic regulation of Protein Activity, by controlling balance of Reverse PTM’s
Which Popular PTM Proteins are reversible?
Acetylation, Methylation, Phosphorylation
List 3 Biological Processes of PTM proteins Controlling their activities?
- Metabolism
- Cellular Signalling
- Gene Transcription
What is PTM a Key Mechanism to Increase? and Why?
Proteomic Diversity , Increases Complexity of Proteome
What are the 3 Structural Changes (Classification) of PTM Proteins?
- Proteolytic Cleavage
- Proline Isomerisation
- Addition of Small Functional Groups
What is Proteolytic Cleavage?
One or Several AA removed from N-Terminus of a Protein. OR Protein Peptide bond Cleaved Internally
What is Proline Isomerisation?
Change in Proline Residue Spatial Confirmation (Between Cis and Trans)
List some Examples of Small functional groups in Addition to PTM Proteins?
Phosphorylation, Acetylation, Methylation, Hydroxylation
What is Protein Phosphorylation?
A Phosphate Group (donated by ATP) is transferred to an Acceptor Protein
What is Protein Phosphorylation Catalyzed by?
Protein Kinase
Give a Example of a Reversible Protein Phosphorylation and its Mechanism?
Pyruvate Dehydrogenase - Activated by NAD+ and ACh, Inhibited by Pyruvate
What Protein is the Cell cycle Controlled by?
Cyclins and their Cyclin Dependant Kinases
What are the 3 most Common Phosphorylated AA’s?
- Serine
- Threonine
- Tyrosine
What does the Phosphorylated AA Tyrosine do?
Binds specific proteins, promoting Protein:Protein Interactions as part of signalling networks
What 2 Methods can be used to Detect Phosphorylated Proteins?
- Proteolysis
2. 2D-gel Electrophoresis
What is Protein Acetylation?
An Acetyl group ( donated by acetyl-CoA) transferred to Acceptor AA lysine
What is Protein Acetylation Catalyzed by?
Protein AcetylTransferase (PAT)
What is the Process of Protein Deacytylation Catalayzed by?
Protein DeACetylase (PDAC)
What do Protein Acetylation target most?
Histones
Why is the Reversible Histone Acytelation important?
Controls Gene Transcription
What is Protein Methylation?
A Methyl group (donated by S-adenosylmethionine) is transferred to an Acceptor Protein
What is Protein Methylation Catalyzed by?
Protein Methyltransferase
What is the Process of Protein Methylation Catalyzed by?
Protein Demethylase
What are the 2 Major AA methylated?
Arginine and Lysine
What is the best example of Protein Methylation?
N-Methylation of arginine and lysine side chains of Histones in Gene Regulation
Give an Example of PTM involving changes in Chemical nature of AA?
Citrullination of Argenine converting it to Citrulline. The Immune system attacks Citrullinated Proteins which can cause Arthiritis
Give an Example of a PTM additional Large Functional Group?
Glycosylation, Fatty Acids
What is Protein Glycosylation?
Process of adding -mono or -poly saccharides to a protein
What are Glycosylated Proteins called?
Glycoproteins
What does Protein Glycosylation, have a significant effect on?
Protein Folding, Conformation, Distribution, Stability and Activity
What are some Biological Functions of Glycosated Proteins?
Protein Stability, Trafficking and Recognition
What two kinds of Olygosaccharides are major structural components of cell surface and secreted proteins?
Carbohydrates in the form of aspargine linked (N-linked) or serine/threonine linked ( O-linked)
What modifications occur to N-linked glycosylation in the ER?
Polysaccharide added as a 14 sugar unit to aspargine residue of the new synthesised polypeptide
What modifications occur to O-linked glycosylation in the Golgi/Cytoplasm?
Sugar added one at a time to hydroxyl group of serine/threonine.
Golgi - secreted proteins
Cytoplasm - cellular proteins
What is Protein PolyUbiquitination?
Small protein containing 76 AA
What is the process of Protein PolyUbiquitination?
Last glycine in Ubiquitin attached to lysine in proteins
What does the attachment to a -mono or -poly ubiquitin chain do to the biological functions of a protein?
- mono = change protein structure
- poly = marks protein for degradation in a proteasome
What 3 enzymes does Ubiquitination require?
E1 - activating enzymes
E2 - conjugating
E3 - ligase
What is a Proteasome and its function?
Large protein complexes inside all Eukaryotes and Archea
Main function to degrade unneeded/damaged proteins
What is the main biological function of PolyUbiquitination and proteasomes?
Remove damage and misfolded proteins
Control lifespan of proteins
Control multicellular processes
What is lipidation?
method to target proteins to membranes in organelles
What are the 4 types of lipidation?
C-Terminal glycosyl (GPI)
N-Terminal Myristoylation
S-Myristoylation
S-Prenylation
How is PTM relevant to medicine?
Defects in PTM and cell signalling - pathobiology
Enzymes controlling PTM - therapeutics
