Which of the following modifications leads to protein degradation ?

Q. Which of the following modifications leads to protein degradation ?

A) Methylation
B) Acetylation
C) Acylation
D) Ubiquitination

... Answer is D). Ubiquitination

Protein ubiquitination is a dynamic multi- faceted post-translational modification involved in nearly all aspects of cukaryotic biology. Once attached to a substrate, the 76-amino acid protein ubiquitin is subjected to further modifications, creating a multitude of distinct signals with distinct cellular outcomes, referred to as the 'ubiquitin code'. Ubiquitin can be ubiquitinated on seven lysine (Lys) residues or on the N-terminus, leading to polyubiquitin chains that can encompass complex topologies. Ubiquitin is a 76-amino acid protein, and as such bears many potential sites for additional post- translational modifications. The key features of ubiquitin are its seven Lys residues, all of which can be ubiquitinated, to give rise to isopeptide-linked ubiquitin chains.