1i74
From Proteopedia
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STREPTOCOCCUS MUTANS INORGANIC PYROPHOSPHATASE
Overview
BACKGROUND: Streptococcus mutans pyrophosphatase (Sm-PPase) is a member of, a relatively uncommon but widely dispersed sequence family (family II) of, inorganic pyrophosphatases. A structure will answer two main questions: is, it structurally similar to the family I PPases, and is the mechanism, similar? RESULTS: The first family II PPase structure, that of homodimeric, Sm-PPase complexed with metal and sulfate ions, has been solved by X-ray, crystallography at 2.2 A resolution. The tertiary fold of Sm-PPase, consists of a 189 residue alpha/beta N-terminal domain and a 114 residue, mixed beta sheet C-terminal domain and bears no resemblance to family I, PPase, even though the arrangement of active site ligands and the residues, that bind them shows significant similarity. The preference for Mn2+ over, Mg2+ in family II PPases is explained by the histidine ligands and, bidentate carboxylate coordination. The active site is located at the, domain interface. The C-terminal domain is hinged to the N-terminal domain, and exists in both closed and open conformations. CONCLUSIONS: The active, site similiarities, including a water coordinated to two metal ions, suggest that the family II PPase mechanism is "analogous" (not, "homologous") to that of family I PPases. This is a remarkable example of, convergent evolution. The large change in C-terminal conformation suggests, that domain closure might be the mechanism by which Sm-PPase achieves, specificity for pyrophosphate over other polyphosphates.
About this Structure
1I74 is a Single protein structure of sequence from Streptococcus mutans with MN, MG and SO4 as ligands. Active as Inorganic diphosphatase, with EC number 3.6.1.1 Full crystallographic information is available from OCA.
Reference
Crystal structure of Streptococcus mutans pyrophosphatase: a new fold for an old mechanism., Merckel MC, Fabrichniy IP, Salminen A, Kalkkinen N, Baykov AA, Lahti R, Goldman A, Structure. 2001 Apr 4;9(4):289-97. PMID:11525166
Page seeded by OCA on Tue Nov 20 17:06:56 2007
