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

被引:25
作者
Conway, ME
Yennawar, N
Wallin, R
Poole, LB
Hutson, SM
机构
[1] Wake Forest Univ, Sch Med, Dept Biochem, Winston Salem, NC 27157 USA
[2] Penn State Univ, Althouse Lab, Dept Biochem & Mol Biol, University Pk, PA 16802 USA
[3] Wake Forest Univ, Sch Med, Dept Internal Med, Winston Salem, NC 27157 USA
来源
BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS | 2003年 / 1647卷 / 1-2期
关键词
aminotransferase; branched chain amino acid; human; mitochondrion; structure; redox-active;
D O I
10.1016/S1570-9639(03)00051-7
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
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. (C) 2003 Elsevier Science B.V. All rights reserved.
引用
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页码:61 / 65
页数:5
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