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Updated: May 11, 2026

In Vitro Analysis of E3 Ubiquitin Ligase Function
06:06

In Vitro Analysis of E3 Ubiquitin Ligase Function

Published on: May 14, 2021

Electron microscopy structure of human APC/C(CDH1)-EMI1 reveals multimodal mechanism of E3 ligase shutdown

Jeremiah J Frye1, Nicholas G Brown, Georg Petzold

  • 11Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.

Nature Structural & Molecular Biology
|May 28, 2013
PubMed

Insights

Early mitotic inhibitor 1 (EMI1) uses its disordered C-terminal domain to inhibit the anaphase-promoting complex/cyclosome (APC/C). This mechanism ensures accurate cell division by blocking substrate binding and ubiquitin chain elongation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The anaphase-promoting complex/cyclosome (APC/C) is a crucial E3 ligase regulating cell division through proteolysis.
  • Early mitotic inhibitor 1 (EMI1) inhibits APC/C(CDH1) during interphase, coordinating DNA synthesis and mitosis.

Purpose of the Study:

  • To elucidate the structural mechanism by which EMI1 inhibits APC/C(CDH1) function.
  • To understand the role of intrinsic disorder in EMI1's inhibitory action.

Main Methods:

  • Hybrid structural approach combining Nuclear Magnetic Resonance (NMR) and electron microscopy.
  • Enzymological assays to assess APC/C(CDH1) activity.

Main Results:

  • EMI1's C-terminal domain inhibits multiple APC/C(CDH1) functions.
  • Disordered elements and a structured zinc-binding domain of EMI1 bind distinct APC/C(CDH1) regions.
  • Synergistic inhibition involves blocking substrate binding and ubiquitin-chain elongation.

Conclusions:

  • Intrinsic structural disorder in EMI1 is key to its inhibitory strategy.
  • A small inhibitory domain effectively shuts down a large molecular machine by binding multiple sites.
  • This provides insight into cell-cycle regulation and molecular machine inhibition.

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