A synchronized substrate-gating mechanism revealed by cubic-core structure of the bovine branched-chain α-ketoacid dehydrogenase complex

Masato Kato, Richard M Wynn, Jacinta L. Chuang, Chad A Brautigam, Myra Custorio, David T Chuang

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

The dihydrolipoamide acyltransferase (E2b) component of the branched-chain α-ketoacid dehydrogenase complex forms a cubic scaffold that catalyzes acyltransfer from S-acyldihydrolipoamide to CoA to produce acyl-CoA. We have determined the first crystal structures of a mammalian (bovine) E2b core domain with and without a bound CoA or acyl-CoA. These structures reveal both hydrophobic and the previously unreported ionic interactions between two-fold-related trimers that build up the cubic core. The entrance of the dihydrolipoamide-binding site in a 30-Å long active-site channel is closed in the apo and acyl-CoA-bound structures. CoA binding to one entrance of the channel promotes a conformational change in the channel, resulting in the opening of the opposite dihydrolipoamide gate. Binding experiments show that the affinity of the E2b core for dihydrolipoamide is markedly increased in the presence of CoA. The result buttresses the model that CoA binding is responsible for the opening of the dihydrolipoamide gate. We suggest that this gating mechanism synchronizes the binding of the two substrates to the active-site channel, which serves as a feed-forward switch to coordinate the E2b-catalyzed acyltransfer reaction.

Original languageEnglish (US)
Pages (from-to)5983-5994
Number of pages12
JournalEMBO Journal
Volume25
Issue number24
DOIs
StatePublished - Dec 13 2006

Keywords

  • Branched-chain α-ketoacid dehydrogenase complex
  • Cubic-core assembly
  • Ionic clamping interaction
  • Maple syrup urine disease
  • Synchronized substrate gating

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

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