title: Mechanism of action and NAD+-binding mode revealed by the crystal structure of L-histidinol dehydrogenase.
abstract: The histidine biosynthetic pathway is an ancient one found in bacteria, archaebacteria, fungi, and plants that converts 5-phosphoribosyl 1-pyrophosphate to l-histidine in 10 enzymatic reactions. This pathway provided a paradigm for the operon, transcriptional regulation of gene expression, and feedback inhibition of a pathway. l-histidinol dehydrogenase (HisD, EC ) catalyzes the last two steps in the biosynthesis of l-histidine: sequential NAD-dependent oxidations of l-histidinol to l-histidinaldehyde and then to l-histidine. HisD functions as a homodimer and requires the presence of one Zn(2+) cation per monomer. We have determined the three-dimensional structure of Escherichia coli HisD in the apo state as well as complexes with substrate, Zn(2+), and NAD(+) (best resolution is 1.7 A). Each monomer is made of four domains, whereas the intertwined dimer possibly results from domain swapping. Two domains display a very similar incomplete Rossmann fold that suggests an ancient event of gene duplication. Residues from both monomers form the active site. Zn(2+) plays a crucial role in substrate binding but is not directly involved in catalysis. The active site residue His-327 participates in acid-base catalysis, whereas Glu-326 activates a water molecule. NAD(+) binds weakly to one of the Rossmann fold domains in a manner different from that previously observed for other proteins having a Rossmann fold.
authors.affiliation: Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount Avenue, Montreal, QC, Canada H4P 2R2.
authors.forename: João A R G
authors.initials: JA
authors.lastname: Barbosa
authors.forename: J
authors.initials: J
authors.lastname: Sivaraman
authors.forename: Yunge
authors.initials: Y
authors.lastname: Li
authors.forename: Robert
authors.initials: R
authors.lastname: Larocque
authors.forename: Allan
authors.initials: A
authors.lastname: Matte
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Schrag
authors.forename: Miroslaw
authors.initials: M
authors.lastname: Cygler
mesh_terms: D000429:Alcohol Oxidoreductases / Q000737:chemistry*; D000595:Amino Acid Sequence; D001665:Binding Sites; D002384:Catalysis; D003001:Cloning, Molecular; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology; D006639:Histidine / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009243:NAD / Q000378:metabolism*; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry
chemical_list: D009243:NAD; D006639:Histidine; D000429:Alcohol Oxidoreductases; C021358:histidinol dehydrogenase; D015032:Zinc