2qb7
From Proteopedia
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Saccharomyces cerevisiae cytosolic exopolyphosphatase, phosphate complex
Overview
Inorganic long-chain polyphosphate is a ubiquitous linear polymer in, biology, consisting of many phosphate moieties linked by phosphoanhydride, bonds. It is synthesized by polyphosphate kinase, and metabolised by a, number of enzymes, including exo- and endopolyphosphatases. The, Saccharomyces cerevisiae gene PPX1 encodes for a 45 kDa, metal-dependent, cytosolic exopolyphosphatase that processively cleaves the terminal, phosphate group from the polyphosphate chain, until inorganic, pyrophosphate is all that remains. PPX1 belongs to the DHH family of, phosphoesterases, which includes: family-2 inorganic pyrophosphatases, found in Gram-positive bacteria; prune, a cyclic AMPase; and RecJ, a, single-stranded DNA exonuclease. We describe the high-resolution X-ray, structures of yeast PPX1, solved using the multiple isomorphous, replacement with anomalous scattering (MIRAS) technique, and its complexes, with phosphate (1.6 A), sulphate (1.8 A) and ATP (1.9 A). Yeast PPX1 folds, into two domains, and the structures reveal a strong similarity to the, family-2 inorganic pyrophosphatases, particularly in the active-site, region. A large, extended channel formed at the interface of the N and, C-terminal domains is lined with positively charged amino acids and, represents a conduit for polyphosphate and the site of phosphate, hydrolysis. Structural comparisons with the inorganic pyrophosphatases and, analysis of the ligand-bound complexes lead us to propose a hydrolysis, mechanism. Finally, we discuss a structural basis for substrate, selectivity and processivity.
About this Structure
2QB7 is a Single protein structure of sequence from Saccharomyces cerevisiae with , , and as ligands. Active as Exopolyphosphatase, with EC number 3.6.1.11 Full crystallographic information is available from OCA.
Reference
The crystal structure of the cytosolic exopolyphosphatase from Saccharomyces cerevisiae reveals the basis for substrate specificity., Ugochukwu E, Lovering AL, Mather OC, Young TW, White SA, J Mol Biol. 2007 Aug 24;371(4):1007-21. Epub 2007 May 31. PMID:17599355
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