Human mitochondrial branched chain aminotransferase: Structural basis for substrate specificity and role of redox active cysteines

Myra E. Conway, Neela Yennawar, Reidar Wallin, Leslie B. Poole, Susan M. Hutson

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

Crystal structures of the fold type IV pyridoxal phosphate (PLP)-dependent human mitochondrial branched chain aminotransferase (hBCATm) reaction intermediates have provided a structural explanation for the kinetically determined substrate specificity of hBCATm. The isoleucine side chain in the ketimine intermediate occupies a hydrophobic binding pocket that can be defined by three surfaces. Modeling of amino acids on the ketimine structure shows that the side chains of nonsubstrate amino acids such as the aromatic amino acids, alanine, or aspartate either are unable to interact through van der Waals' interactions or have steric clashes. The structural and biochemical basis for the sensitivity of the mammalian BCAT to reducing agents has also been elucidated. Two cysteine residues in hBCATm, Cys315 and Cys318 (CXXC), are part of a redox-controlled mechanism that can regulate hBCATm activity. The residues surrounding Cys315 and Cys318 show considerable sequence conservation in the prokaryotic and eukaryotic BCAT sequences, however, the CXXC motif is found only in the mammalian proteins. The results suggest that the BCAT enzymes may join the list of enzymes that can be regulated by redox status.

Original languageEnglish (US)
Pages (from-to)61-65
Number of pages5
JournalBiochimica et Biophysica Acta - Proteins and Proteomics
Volume1647
Issue number1-2
DOIs
StatePublished - Apr 11 2003

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Biophysics
  • Biochemistry
  • Molecular Biology

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