Misfolded or unnecessary proteins can be a hazard to the livelihood of the entir
ID: 81744 • Letter: M
Question
Misfolded or unnecessary proteins can be a hazard to the livelihood of the entire cell, such proteins are often marked with ubiquitin for disposal. Compare two different types of ubiquitylation (or ubiquitin-like modification) you have learned about in class, for each describe where on the protein it occurs and what signal this modification confers. For one of these, describe what would happen to the protein if the key deubiquitylating enzyme for this system were altered to be more active than normal.
Explanation / Answer
when a substrate protein adds to ubiquitin it's called ubiquitination or ubiquitylation.It is carried out in three main steps: activation, conjugation and ligation and performed by ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s) and ubiquitin ligases (E3s), respectively.Ubiquitination effects cellular process by regulating the degradation of proteins via the proteasome and lysosome which are mediated by different types of substrate ubiquitination.
Types:
1.Monoubiquitination:
It is a process where one ubiquitin molecule adds to one substrate protein residue. Monoubiquitination effects cellular processes such as membrane trafficking, endocytosis and viral budding.
2.Polyubiquitin chains:
Polyubiquitination is the formation of a ubiquitin chain on a single lysine residue on the substrate protein.Ubiquitin has seven lysine residues and an N-terminus that serves as points of ubiquitination; they are K6, K11, K27, K29, K33, K48, K63 and M1, respectively.