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#E3 ligase

2 public questions tagged with this topic.

Cell Cycle Regulation

Which molecule directly targets p27 for ubiquitin-mediated degradation?

Abundance of p27 is controlled post-translationally rather than transcriptionally, illustrating CDK-regulated proteolysis that sharpens G1/S transition. Late in G1, cyclin E-CDK2 phosphorylates p27 intrinsically disordered C-terminus at threonine 187. This phosphate forms high-affinity interaction with WD40 domain of Skp2, F-box protein assembled into SCF-Skp2 E3 ligase with Skp1 adaptor, Cullin1 scaffold, Rbx1 RING finger recruiting Ubc3 E2 enzyme, plus Cks1 cofactor that bridges CDK and F-box. SCF catalyzes formation of K48-linked polyubiquitin chains on p27 lysines, marking it for rapid deg

Ref: Carrano et al., Nature Cell Biology 1999, SCF-Skp2 Targets p27. Alberts 7th ed., Chapter 3.

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Protein

The primary role of E3 ligase in ubiquitination is:

Recognition of target proteins and transfer of ubiquitin is the accurate answer because it correctly identifies the biological function or role described in this question. In Protein Degradation, understanding the specific functions of molecules, enzymes, or structures is fundamental. Recognition of target proteins and transfer of ubiquitin fulfills this particular biological role through its specific structural properties, biochemical activity, or physiological mechanism. The other options (Activation of ubiquitin, Conjugation of ubiquitin, and Hydrolysis of ubiquitin-protein bonds) serve dif

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4

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