Protein processing Flashcards
What is protein sorting?
It is how proteins know where to go in the cell
Where is regulated secretion seen?
In the endocrine, exocrine and neurocrine systems
If ribosomes attach to the ER membrane, where is the protein destined for?
The cell membrane or a secretory pathway via co-translational insertion
Ribosomes remain cystolic if….
The protein is destined for the cytosol, or post-translational import into organelles
What are the four requirements for protein sorting?
- Intrinsic signal in the protein
- Specific receptors to recognise the signal
- Translation machinery
- Energy to transfer the protein to its new place
At which terminus are signal sequences found in secretory proteins?
The N-terminus
Which enzyme in the ER assists with forming disulphide bonds?
Protein disulphide isomerase
N-linked glycosylation takes place in which organelle? And to which amino acid are sugars added?
It takes place in the ER. Sugars are added to a asparagine side chain
What is the function of peptidyl-propyl isomerases?
It is there function to accelerate the interconversion of cis- and tran- isomers of proline residues. This greatly facilitates rapid protein folding.
What is O-linked glycosylation?
It is the modification of the hydroxyl groups on serine and threonine. Glycosyl transferase builds up a sugar chain from nucleotide sugar substrates. This takes place in the Golgi
What enzyme catalyses the hydroxylation of proline and lysine residues in collagen?
Propyl hydroxylase
What is added to the hydroxylysine residues of collagen?
Galactose
Where does the synthesis and modification of collagen take place?
In the rough ER
Tropocollagen is made of?
3 alpha chains
The conversion of …. to …. occurs extracellularly via procollagen peptidases
Procollagen to tropocollagen
