Three classes of proteins are responsible for tagging proteins destined for degradation by the proteasome complex....

Three classes of proteins are responsible for tagging proteins destined for degradation by the proteasome complex. Name the enzymes and briefly describe the function of each enzyme involved.

Expert Solution

Tagging of small peptide to the protein for degradation is called ubiquitination.

Three enzymes are needed for this process i.e.,

E1 ( ubiquitin activating enzyme) : this enzyme activates ubiquitin protein by covalently attacking to active site cysteine residue. It is energy requiring process hence, ATP is also involved. This results in thio-ester linkage between C-terminal COOH of ubiquitin and cysteine sulfhydryl group.

E2 (Ubiquitin conjugating enzyme): thisenzyme help in transfer of Ubiquitin from E1 to active site of cysteine of E2 via trans-estrification. E2 enzyme carries Ubiquitin to lysine residue in the target enzyme.

E3 (Ubiquitin ligases): this enzyme selectively recognises the target protein/condemned protein and transfers Ubiquitin from E2 to lysine residue of the target protein. Ubiquitinylated cascade creates isopeptide bond between lysine residue of target protein and C terminal glycine of E3.

gladiator answered 1 year ago

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