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Crystal structure of histamine dehydrogenase from Nocardioides simplex.

ABSTRACT: Histamine dehydrogenase (HADH) isolated from Nocardioides simplex catalyzes the oxidative deamination of histamine to imidazole acetaldehyde. HADH is highly specific for histamine, and we are interested in understanding the recognition mode of histamine in its active site. We describe the first crystal structure of a recombinant form of HADH (HADH) to 2.7-A resolution. HADH is a homodimer, where each 76-kDa subunit contains an iron-sulfur cluster ([4Fe-4S](2+)) and a 6-S-cysteinyl flavin mononucleotide (6-S-Cys-FMN) as redox cofactors. The overall structure of HADH is very similar to that of trimethylamine dehydrogenase (TMADH) from Methylotrophus methylophilus (bacterium W3A1). However, some distinct differences between the structure of HADH and TMADH have been found. Tyr(60), Trp(264), and Trp(355) provide the framework for the "aromatic bowl" that serves as a trimethylamine-binding site in TMADH is comprised of Gln(65), Trp(267), and Asp(358), respectively, in HADH. The surface Tyr(442) that is essential in transferring electrons to electron-transfer flavoprotein (ETF) in TMADH is not conserved in HADH. We use this structure to propose the binding mode for histamine in the active site of HADH through molecular modeling and to compare the interactions to those observed for other histamine-binding proteins whose structures are known.

SUBMITTER: Reed T

PROVIDER: S-EPMC2919140 | biostudies-literature | 2010 Aug

REPOSITORIES: biostudies-literature

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Crystal structure of histamine dehydrogenase from Nocardioides simplex.

Reed Timothy T Lushington Gerald H GH Xia Yan Y Hirakawa Hidehiko H Travis DeAnna M DM Mure Minae M Scott Emily E EE Limburg Julian J

The Journal of biological chemistry 20100610 33

Histamine dehydrogenase (HADH) isolated from Nocardioides simplex catalyzes the oxidative deamination of histamine to imidazole acetaldehyde. HADH is highly specific for histamine, and we are interested in understanding the recognition mode of histamine in its active site. We describe the first crystal structure of a recombinant form of HADH (HADH) to 2.7-A resolution. HADH is a homodimer, where each 76-kDa subunit contains an iron-sulfur cluster ([4Fe-4S](2+)) and a 6-S-cysteinyl flavin mononuc ...[more]

PMID: 20538584

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Project description:BackgroundAs the third enzyme of the pentose phosphate pathway, 6-phosphogluconate dehydrogenase (6PGDH) is the main generator of cellular NADPH. Both thioredoxin reductase and glutathione reductase require NADPH as the electron donor to reduce oxidized thioredoxin or glutathione (GSSG). Since thioredoxin and GSH are important antioxidants, it is not surprising that 6PGDH plays a critical role in protecting cells from oxidative stress. Furthermore the activity of 6PGDH is associated with several human disorders including cancer and Alzheimer's disease. The 3D structural investigation would be very valuable in designing small molecules that target this enzyme for potential therapeutic applications.ResultsThe crystal structure of 6-phosphogluconate dehydrogenase (6PGDH/Gnd1) from Saccharomyces cerevisiae has been determined at 2.37 A resolution by molecular replacement. The overall structure of Gnd1 is a homodimer with three domains for each monomer, a Rossmann fold NADP+ binding domain, an all-alpha helical domain contributing the majority to hydrophobic interaction between the two subunits and a small C-terminal domain penetrating the other subunit. In addition, two citrate molecules occupied the 6PG binding pocket of each monomer. The intact Gnd1 had a Km of 50 +/- 9 microM for 6-phosphogluconate and of 35 +/- 6 microM for NADP+ at pH 7.5. But the truncated mutants without the C-terminal 35, 39 or 53 residues of Gnd1 completely lost their 6PGDH activity, despite remaining the homodimer in solution.ConclusionThe overall tertiary structure of Gnd1 is similar to those of 6PGDH from other species. The substrate and coenzyme binding sites are well conserved, either from the primary sequence alignment, or from the 3D structural superposition. Enzymatic activity assays suggest a sequential mechanism of catalysis, which is in agreement with previous studies. The C-terminal domain of Gnd1 functions as a hook to further tighten the dimer, but it is not necessary for the dimerization. This domain also works as a lid on the substrate binding pocket to control the binding of substrate and the release of product, so it is indispensable for the 6PGDH activity. Moreover, the co-crystallized citrate molecules, which mimic the binding mode of the substrate 6-phosphogluconate, provided us a novel strategy to design the 6PDGH inhibitors.

Dataset Information

Crystal structure of histamine dehydrogenase from Nocardioides simplex.

Publications

Crystal structure of histamine dehydrogenase from Nocardioides simplex.

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