APC2 cullin protein and APC11 RING protein comprise the minimal ubiquitin ligase module of the anaphase-promoting complex

Z. Tang, B. Li, R. Bharadwaj, H. Zhu, E. Özkan, K. Hakala, J. Deisenhofer, H. Yu

Research output: Contribution to journalArticle

136 Scopus citations

Abstract

In mitosis, the anaphase-promoting complex (APC) regulates the onset of sister-chromatid separation and exit from mitosis by mediating the ubiquitination and degradation of the securin protein and mitotic cyclins. With the use of a baculoviral expression system, we have reconstituted the ubiquitin ligase activity of human APC. In combination with Ubc4 or UbcH10, a heterodimeric complex of APC2 and APC11 is sufficient to catalyze the ubiquitination of human securin and cyclin B1. However, the minimal APC2/11 ubiquitin ligase module does not possess substrate specificity, because it also ubiquitinates the destruction box deletion mutants of securin and cyclin B1. Both APC11 and UbcH10 bind to the C-terminal cullin homology domain of APC2, whereas Ubc4 interacts with APC11 directly. Zn2+-binding and mutagenesis experiments indicate that APC11 binds Zn2+ at a 1:3 M ratio. Unlike the two Zn2+ ions of the canonical RING-finger motif, the third Zn2+ ion of APC11 is not essential for its ligase activity. Surprisingly, with Ubc4 as the E2 enzyme, Zn2+ ions alone are sufficient to catalyze the ubiquitination of cyclin B1. Therefore, the Zn2+ ions of the RING finger family of ubiquitin ligases may be directly involved in catalysis.

Original languageEnglish (US)
Pages (from-to)3839-3851
Number of pages13
JournalMolecular biology of the cell
Volume12
Issue number12
DOIs
StatePublished - 2001

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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