Publications

• Structural studies of the catalytic reaction pathway of a hyperthermophilic histidinol-phosphate aminotransferase.

  Fernandez F.J., Vega M.C., Lehmann F., Sandmeier E., Gehring H., Christen P., Wilmanns M.

  In histidine biosynthesis, histidinol-phosphate aminotransferase catalyzes the transfer of the amino group from glutamate to imidazole acetol-phosphate producing 2-oxoglutarate and histidinol phosphate. In some organisms such as the hyperthermophile Thermotoga maritima, specific tyrosine and aroma ... >> More

  In histidine biosynthesis, histidinol-phosphate aminotransferase catalyzes the transfer of the amino group from glutamate to imidazole acetol-phosphate producing 2-oxoglutarate and histidinol phosphate. In some organisms such as the hyperthermophile Thermotoga maritima, specific tyrosine and aromatic amino acid transaminases have not been identified to date, suggesting an additional role for histidinol-phosphate aminotransferase in other transamination reactions generating aromatic amino acids. To gain insight into the specific function of this transaminase, we have determined its crystal structure in the absence of any ligand except phosphate, in the presence of covalently bound pyridoxal 5'-phosphate, of the coenzyme histidinol phosphate adduct, and of pyridoxamine 5'-phosphate. The enzyme accepts histidinol phosphate, tyrosine, tryptophan, and phenylalanine, but not histidine, as substrates. The structures provide a model of how these different substrates could be accommodated by histidinol-phosphate aminotransferase. Some of the structural features of the enzyme are more preserved between the T. maritima enzyme and a related threonine-phosphate decarboxylase from S. typhimurium than with histidinol-phosphate aminotransferases from different organisms. << Less

  J. Biol. Chem. 279:21478-21488(2004) [PubMed] [EuropePMC]

• Crystal structure of histidinol phosphate aminotransferase (HisC) from Escherichia coli, and its covalent complex with pyridoxal-5'-phosphate and L-histidinol phosphate.

  Sivaraman J., Li Y., Larocque R., Schrag J.D., Cygler M., Matte A.

  The biosynthesis of histidine is a central metabolic process in organisms ranging from bacteria to yeast and plants. The seventh step in the synthesis of histidine within eubacteria is carried out by a pyridoxal-5'-phosphate (PLP)-dependent l-histidinol phosphate aminotransferase (HisC, EC 2.6.1.9 ... >> More

  The biosynthesis of histidine is a central metabolic process in organisms ranging from bacteria to yeast and plants. The seventh step in the synthesis of histidine within eubacteria is carried out by a pyridoxal-5'-phosphate (PLP)-dependent l-histidinol phosphate aminotransferase (HisC, EC 2.6.1.9). Here, we report the crystal structure of l-histidinol phosphate aminotransferase from Escherichia coli, as a complex with pyridoxamine-5'-phosphate (PMP) at 1.5 A resolution, as the internal aldimine with PLP, and in a covalent, tetrahedral complex consisting of PLP and l-histidinol phosphate attached to Lys214, both at 2.2 A resolution. This covalent complex resembles, in structural terms, the gem-diamine intermediate that is formed transiently during conversion of the internal to external aldimine.HisC is a dimeric enzyme with a mass of approximately 80 kDa. Like most PLP-dependent enzymes, each HisC monomer consists of two domains, a larger PLP-binding domain having an alpha/beta/alpha topology, and a smaller domain. An N-terminal arm contributes to the dimerization of the two monomers. The PLP-binding domain of HisC shows weak sequence similarity, but significant structural similarity with the PLP-binding domains of a number of PLP-dependent enzymes. Residues that interact with the PLP cofactor, including Tyr55, Asn157, Asp184, Tyr187, Ser213, Lys214 and Arg222, are conserved in the family of aspartate, tyrosine and histidinol phosphate aminotransferases. The imidazole ring of l-histidinol phosphate is bound, in part, through a hydrogen bond with Tyr110, a residue that is substituted by Phe in the broad substrate specific HisC enzymes from Zymomonas mobilis and Bacillus subtilis. Comparison of the structures of the HisC internal aldimine, the PMP complex and the HisC l-histidinol phosphate complex reveal minimal changes in protein or ligand structure. Proton transfer, required for conversion of the gem-diamine to the external aldimine, does not appear to be limited by the distance between substrate and lysine amino groups. We propose that the tetrahedral complex has resulted from non-productive binding of l-histidinol phosphate soaked into the HisC crystals, resulting in its inability to be converted to the external aldimine at the HisC active site. << Less

  J. Mol. Biol. 311:761-776(2001) [PubMed] [EuropePMC]

• Insights into the structural basis of substrate recognition by histidinol-phosphate aminotransferase from Corynebacterium glutamicum.

  Marienhagen J., Sandalova T., Sahm H., Eggeling L., Schneider G.

  Histidinol-phosphate aminotransferase (HisC) is a pyridoxal 5'-phosphate-dependent enzyme that catalyzes the reversible transamination reaction between histidinol phosphate (His-P) and 2-oxoglutarate (O-Glu). The crystal structures of apo histidinol-phosphate aminotransferase from Corynebacterium ... >> More

  Histidinol-phosphate aminotransferase (HisC) is a pyridoxal 5'-phosphate-dependent enzyme that catalyzes the reversible transamination reaction between histidinol phosphate (His-P) and 2-oxoglutarate (O-Glu). The crystal structures of apo histidinol-phosphate aminotransferase from Corynebacterium glutamicum, of the internal PLP aldimine adduct and of a pyridoxamine 5-phosphate-enzyme complex were determined at resolutions of 2.2, 2.1 and 1.8 A, respectively. Residues important for substrate specificity were identified by modelling His-P into the active site and comparison with crystal structures of HisC from Thermotoga maritima and Escherichia coli. Four of the residues lining the substrate-binding pocket were studied by site-directed mutagenesis. Kinetic analysis of the Tyr21Phe mutant suggested that the hydrogen bond between the side chain of this residue and the phosphate group of His-P is important for recognition of the natural substrate and discrimination against other potential amino donors such as phenylalanine and leucine. The mutagenesis studies further indicated that residue Asn99 does not contribute to the specific recognition of the amino-acid donor, but may be involved in binding of the phosphate group of pyridoxal 5'-phosphate. The conserved residues Tyr123 and Tyr257 interact with the substrate through van der Waals interactions and their potential for hydrogen-bonding interactions is not utilized in substrate recognition, as the corresponding phenylalanine mutants show only a moderate effect on the catalytic efficiency kcat/Km. << Less

  Acta Crystallogr D Biol Crystallogr 64:675-685(2008) [PubMed] [EuropePMC]