Active-site characterization of Candida boidinii formate dehydrogenase

NAD+-dependent formate dehydrogenase (FDH) from Candida boidinii was cloned and expressed to a high level in Escherichia coli (20% of soluble E. coli protein). Molecular modelling studies were used to create a three-dimensional model of C. boidinii FDH, based on a known structure of the Pseudomonas...

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Bibliographic Details
Published in:Biochemical journal 2001-03, Vol.354 (Pt 2), p.455-463
Main Authors: Labrou, N E, Rigden, D J
Format: Article
Language:English
Subjects:
Binding Sites
Candida - enzymology
Catalysis
Cloning, Molecular
Escherichia coli
Formate Dehydrogenases - chemistry
Formate Dehydrogenases - genetics
Formate Dehydrogenases - metabolism
Formates - metabolism
Hydrogen-Ion Concentration
Kinetics
Models, Molecular
Molecular Conformation
Molecular Sequence Data
Mutagenesis, Site-Directed
NAD - metabolism
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Summary:NAD+-dependent formate dehydrogenase (FDH) from Candida boidinii was cloned and expressed to a high level in Escherichia coli (20% of soluble E. coli protein). Molecular modelling studies were used to create a three-dimensional model of C. boidinii FDH, based on a known structure of the Pseudomonas sp. 101 enzyme. This model was used for investigating the catalytic mechanism by site-directed mutagenesis. Eleven forms of C. boidinii FDH were characterized by steady-state kinetic analysis: the wild type as well as 10 mutants involving single (Phe-69-Ala, Asn-119-His, Ile-175-Ala, Gln-197-Leu, Arg-258-Ala, Gln-287-Glu and His-311-Gln) and double amino acid substitutions (Asn-119-His/His-311-Gln, Gln-287-Glu/His-311-Gln and Gln-287-Glu/Pro-288-Thr). The kinetic results of the mutant enzymes provide the first experimental support that hydrophobic patches, formed by Phe-69 and Ile-175, destabilize substrates and stabilize products. Also, the key role of Arg-258 in stabilization of the negative charge on the migrating hydride was established. Asn-119, besides being an anchor group for formate, also may comprise one of the hinge regions around which the two domains shift on binding of NAD+. The more unexpected results, obtained for the His-311-Gln and Gln-287-Glu/His-311-Gln mutants, combined with molecular modelling, suggest that steric as well as electrostatic properties of His-311 are important for enzyme function. An important structural role has also been attributed to cis-Pro-288. This residue may provide the key residues Gln-287 and His-311 with the proper orientation for productive binding of formate.
ISSN:0264-6021
1470-8728
DOI:10.1042/0264-6021:3540455