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CRYSTAL STRUCTURE OF THE COMPLEX OF 3-ISOPROPYLMALATE DEHYDROGENASE FROM THIOBACILLUS FERROOXIDANS WITH 3-ISOPROPYLMALATE
Structural highlights
FunctionLEU3_ACIFR Catalyzes the oxidation of 3-carboxy-2-hydroxy-4-methylpentanoate (3-isopropylmalate) to 3-carboxy-4-methyl-2-oxopentanoate. The product decarboxylates to 4-methyl-2 oxopentanoate. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBACKGROUND: 3-Isopropylmalate dehydrogenase (IPMDH) and isocitrate dehydrogenase (ICDH) belong to a unique family of bifunctional decarboxylating dehydrogenases. Although the ICDH dimer catalyzes its reaction under a closed conformation, known structures of the IPMDH dimer (without substrate) adopt a fully open or a partially closed form. Considering the similarity in the catalytic mechanism, the IPMDH dimer must be in a fully closed conformation during the reaction. A large conformational change should therefore occur upon substrate binding. RESULTS: We have determined the crystal structure of IPMDH from Thiobacillus ferrooxidans (Tf) complexed with 3-isopropylmalate (IPM) at 2.0 A resolution by the molecular replacement method. The structure shows a fully closed conformation and the substrate-binding site is quite similar to that of ICDH except for a region around the gamma-isopropyl group. The gamma group is recognized by a unique hydrophobic pocket, which includes Glu88, Leu91 and Leu92 from subunit 1 and Val193' from subunit 2. CONCLUSIONS: A large movement of domain 1 is induced by substrate binding, which results in the formation of the hydrophobic pocket for the gamma-isopropyl moiety of IPM. A glutamic acid in domain 1, Glu88, participates in the formation of the hydrophobic pocket. The C beta and C gamma atoms of Glu88 interact with the gamma-isopropyl moiety of IPM and are central to the recognition of substrate. The acidic tip of Glu88 is likely to interact with the nicotinamide mononucleotide (NMN) ribose of NAD+ in the ternary complex. This structure clearly explains the substrate specificity of IPMDH. Structure of 3-isopropylmalate dehydrogenase in complex with 3-isopropylmalate at 2.0 A resolution: the role of Glu88 in the unique substrate-recognition mechanism.,Imada K, Inagaki K, Matsunami H, Kawaguchi H, Tanaka H, Tanaka N, Namba K Structure. 1998 Aug 15;6(8):971-82. PMID:9739088[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences | ||||||||||||||||||||
