Molecular mechanism for regulation of the human mitochondrial branched-chain α-ketoacid dehydrogenase complex by phosphorylation

R. Max Wynn, Masato Kato, Mischa MacHius, Jacinta L. Chuang, Jun Li, Diana R. Tomchick, David T. Chuang

Research output: Contribution to journalArticle

44 Scopus citations

Abstract

The human mitochondrial branched-chain α-ketoacid dehydrogenase complex (BCKDC) is a 4 MDa macromolecular machine comprising three catalytic components (E1b, E2b, and E3), a kinase, and a phosphatase. The BCKDC overall activity is tightly regulated by phosphorylation in response to hormonal and dietary stimuli. We report that phosphorylation of Ser292-α in the E1b active site channel results in an order-to-disorder transition of the conserved phosphorylation loop carrying the phosphoryl serine. The conformational change is triggered by steric clashes of the phosphoryl group with invariant His291-α that serves as an indispensable anchor for the phosphorylation loop through bound thiamin diphosphate. Phosphorylation of Ser292-α does not severely impede the E1b-dependent decarboxylation of α-ketoacids. However, the disordered loop conformation prevents phosphorylated E1b from binding the E2b lipoyl-bearing domain, which effectively shuts off the E1b-catalyzed reductive acylation reaction and therefore completely inactivates BCKDC. This mechanism provides a paradigm for regulation of mitochondrial α-ketoacid dehydrogenase complexes by phosphorylation.

Original languageEnglish (US)
Pages (from-to)2185-2196
Number of pages12
JournalStructure
Volume12
Issue number12
DOIs
StatePublished - Dec 1 2004

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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