Post-translational modifications

Protein targeting/sorting

moving proteins from the cytosol to other cellular destinations after they are synthesised

What is a signal sequence?

it is a sequence that directs the protein it is attached to towards its destination in the cell

How long is a signal sequence? Where is it located?

it is 15-30 amino acids long, found at the N terminal

Are all signal sequences the same?

no, the signal sequences are different depending on where the protein is supposed to go

How is the signal sequence removed?

It is cleaved by signal peptidase

What is a protease?

An enzyme that catalyses the breakdown of proteins into smaller polypeptides

What is proteolytic processing?

When a protease cleaves a protein to modify its activity

What is an example of proteolytic processing?

Conversion of preproinsulin into insulin

What steps are taken in the processing of insulin

removal of the signal sequence, formation of the disulfide bonds, removal of the C polypeptide chain

What are 3 types of post-translational modifications that modify the individual amino acid?

Phosphorylation, hydroxylation, glycosylation

What is an example of a protein (and the amino acids) that goes through hydroxylation?

collagen, specifically proline (→hydroxyproline) and lysine (→hydroxylysine)