Post Translational Modifications, protein Targetting And Collagen Biosynthesis Flashcards
How many helixes are on collagen
3
Every third amino acid would be glycine
Also large amount is Serine and proline
Where are the hydrogen bonds and why would then be there
Within the helix structure
Would allow increased stability in the molecule
What would be needed for hydroxylation
Vitamins c
What does hydroxylation help with
Thermostability
What are the two terminals that’s would be found within the procollagen
N terminal
C terminal
What terminal would have the disulfide bonds
The C terminal
What causes scurvy and what are some of the symptoms
Deficiency of vitamin c or ascortic acid
Weakness, poor healing, gum disease, anaemia
What is osteogenesis imperfecta
The mutation in the COL1A1 or COL1A2 genes
Would have glycine substituted for a bulkier amino acid
Not having the correct folding of the molecule
What is elders-Danlos syndrome
Stretchy skin
Mutation in the collagen type V or deficiency in the Lysyl oxidase enzymes (not allowing the cores bridges to form)
Would effect the extra cellular cleavage, the cross link formation and stability would be effected
What are the steps that would allow the formation of the cross bridges
Lysine residues
Lysyl oxidase and oxygen forming the aldehyde derivatives
Formation of the Aldo’s cross links (thought to be spontaneous)
What cleaves the terminals on pro-collagen to form tropocollagen
Collagen peptidase
What is needed for collagen to enter the endoplasmic reticulum
The signalling function that would soon be cleaved off (signal pepsidase)
What stages would occur I the extracellular
Cleavage of the n and c terminals to for tropocollagen
The formation of the cross bridges
How would preproinsulin go to proinsulin
Cleavage of the signalling function
Formation of the disulfide bonds
How would proinsulin go to insulin
The cleavage of the C-terminal in the Golgi apparatus
What enzyme is used for the formation of the disulfide bonds
Protein disulphide isomerase
How can the formation of the disulphide bonds be seen as a redox reaction
At first the substrate would be reduced (contains H+) the enzyme would be oxidised.
When the bond formed the substrate would be oxidised as would lose H+ but the enzyme would be reduced as would gain the H+ from the substrate
What happens when a protein is misfolded and why
Move to the cytosol and would be degraded
If not would build, making it toxic
Damage of the ER
How would proteins move into the cells from free ribosomes
Signalling element on amino acids (SKL- serine, lysine, leucine)
Attaches to the receptor PTSIR (cytosolic protein receptor)
Would attach to the protein tetramer
Move it to the membrane receptor protein (pex14p)
PTSIR and the tetramer would then move through the membrane
Complex released and the PTSIR moves out (by atp hydrolysis)
Reused
How would proteins enter the ER across the membrane
The ribosome would attach to the SRPs (signal receptor proteins) these are GTPS
Attaches to another SRP on the membrane
The ribosome soon released (GTP GOES TO GDP AND PI)
This allows the translocon to open
Signal function cleaved off (signal peptidase)
What would change if a protein was being made FOR the membrane
Added a signal anchor transfer sequence
What is O-linked glycosylation
Sugar would be added to the OH group of serine of Theronine
What is N-linked glycosylation
The sugar would be added to the amino acid (asparagine)
What are the four things required for protein sorting
Signalling function
Receptor
Translocation machinery
The energy (ATP)
What re the functions of the endoplasmic reticulum
Hydroxylation
Glycosylation
Proper folding of the protein
Insertion of the protein into the membrane
Protein cleavage
What can cause protein misfolding
Mutation
Protein incorrectly associated with a subunit
Protein can also get stuck in its misfolded form
What are the functions of the chaperones
Monitor the misfolding
Increase transcription of the chaperones
Decrease translation of the protein
Retain the misfolded protein on the ER
What is the difference between the Cis face and the Trans face of the Golgi
Cis face is the side closest to the ER and the nucleus
Trans face is the side that is the closest to the membrane of the cell
How would the level of C terminal cleaved be different in diabetics
Would be low
Diabetics would not produce their own insulin
So would not have a lot of the cleaving of the C terminal
What is the difference between PEX14 and PTS1R
Both would be used for the transport of a protein into the membrane
PEX14 would be the receptor on the perioxisome
PTS1R would be the complex that would recognise the signalling sequence (SKL in the case of catalase) and carry the protein through the membrane
What protein does the SKL (serine leucine lysine) sequence refer too
Catalase
Why is important glycosylation
Protein stability
Protein folding
Deficiency in N-linked (one the amine of asparagine) would lead to inherited diseases (congenital disorders or glycosylation)
Allows interaction with other proteins
Where does N-linked glycosylation happen
In the ER
Where does O-linked glycosylation happen
In the golgi
What amino acids normally undergo hydroxylation
Lysine and proline (in the ER)
Can form proline hydroxylase
