Modeling substrate binding in Thermus thermophilus isopropylmalate dehydrogenase.
The Thermus thermophilus 3-isopropylmalate dehydrogenase (IPMDH) and Escherichia coli isocitrate dehydrogenase (ICDH) are two functionally and evolutionarily related enzymes with distinct substrate specificities. To understand the determinants of substrate specificities of the two proteins, the substrate and coenzyme in IPMDH were docked into their respective binding sites based on the published structure for apo IPMDH and its sequence and structural homology to ICDH. This modeling study suggests that (1) the substrate and coenzyme (NAD) binding modes of IPMDH are significantly different from those of ICDH, (2) the interactions between the substrates and coenzymes help explain the differences in substrate specificities of IPMDH and ICDH, and (3) binding of the substrate and coenzyme should induce a conformational change in the structure of IPMDH.
Zhang
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Department of Molecular and Cell Biology, University of California, Berkeley 94720, USA.
Koshland
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D050539:3-Isopropylmalate Dehydrogenase; D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D003196:Computer Graphics; D017124:Conserved Sequence; D004926:Escherichia coli / Q000201:enzymology; D007521:Isocitrate Dehydrogenase / Q000737:chemistry / Q000378:metabolism; D008293:Malates / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013379:Substrate Specificity; D016963:Thermus thermophilus / Q000201:enzymology*
D008293:Malates; C025313:beta-isopropylmalate; D000429:Alcohol Oxidoreductases; D007521:Isocitrate Dehydrogenase; D050539:3-Isopropylmalate Dehydrogenase