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Crystal structure of the regulatory subunit H of the V-type ATPase of Saccharomyces cerevisiae.

ABSTRACT: In contrast to the F-type ATPases, which use a proton gradient to generate ATP, the V-type enzymes use ATP to actively transport protons into organelles and extracellular compartments. We describe here the structure of the H-subunit (also called Vma13p) of the yeast enzyme. This is the first structure of any component of a V-type ATPase. The H-subunit is not required for assembly but plays an essential regulatory role. Despite the lack of any apparent sequence homology the structure contains five motifs similar to the so-called HEAT or armadillo repeats seen in the importins. A groove, which is occupied in the importins by the peptide that targets proteins for import into the nucleus, is occupied here by the 10 amino-terminal residues of subunit H itself. The structural similarity suggests how subunit H may interact with the ATPase itself or with other proteins. A cleft between the amino- and carboxyl-terminal domains also suggests another possible site of interaction with other factors.

SUBMITTER: Sagermann M

PROVIDER: S-EPMC34635 | biostudies-literature | 2001 Jun

REPOSITORIES: biostudies-literature

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Crystal structure of the regulatory subunit H of the V-type ATPase of Saccharomyces cerevisiae.

Sagermann M M Stevens T H TH Matthews B W BW

Proceedings of the National Academy of Sciences of the United States of America 20010601 13

In contrast to the F-type ATPases, which use a proton gradient to generate ATP, the V-type enzymes use ATP to actively transport protons into organelles and extracellular compartments. We describe here the structure of the H-subunit (also called Vma13p) of the yeast enzyme. This is the first structure of any component of a V-type ATPase. The H-subunit is not required for assembly but plays an essential regulatory role. Despite the lack of any apparent sequence homology the structure contains fiv ...[more]

PMID: 11416198

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Project description:BACKGROUND: As 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. RESULTS: The 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. CONCLUSION: The 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 the regulatory subunit H of the V-type ATPase of Saccharomyces cerevisiae.

Publications

Crystal structure of the regulatory subunit H of the V-type ATPase of Saccharomyces cerevisiae.

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