2or2

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Structure of the W47A/W242A Mutant of Bacterial Phosphatidylinositol-Specific Phospholipase C

Overview

The crystal structure of the W47/242A mutant of, phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus, thuringiensis has been solved to 1.8 A resolution. The W47/242A mutant is, an interfacially-challenged enzyme, and it has been proposed that one or, both tryptophan side chains serve as membrane interfacial anchors (Feng et, al. (2002) J. Biol. Chem. 277, 19867-75). The crystal structure supports, this hypothesis. Relative to the crystal structure of the closely-related, (97% identity) wild-type PI-PLC from B. cereus, significant conformational, differences occur at the membrane-binding interfacial region rather than, the active site. The TrpAla mutations not only remove the, membrane-partitioning aromatic side chains but also perturb the, conformations of the so-called helix B and rim loop regions, both of which, are implicated in interfacial binding. The crystal structure also reveals, a homodimer, the first such observation for a bacterial PI-PLC, with, pseudo 2-fold symmetry. The symmetric dimer interface is stabilized by, hydrophobic and hydrogen-bonding interactions, contributed primarily by a, central swath of aromatic residues arranged in a quasi-herringbone, pattern. Evidence that interfacially-active wild-type PI-PLC enzymes may, dimerize in the presence of phosphatidylcholine vesicles is provided by, fluorescence quenching of PI-PLC mutants with pyrene-labeled cysteine, residues. The combined data suggest that wild-type PI-PLC can form similar, homodimers, anchored to the interface by the tryptophan and neighboring, membrane-partitioning residues.

About this Structure

2OR2 is a Single protein structure of sequence from Bacillus thuringiensis. Active as Phosphatidylinositol diacylglycerol-lyase, with EC number 4.6.1.13 Full crystallographic information is available from OCA.

Reference

Dimer structure of an interfacially impaired phosphatidylinositol-specific phospholipase C., Shao C, Shi X, Wehbi H, Zambonelli C, Head JF, Seaton BA, Roberts MF, J Biol Chem. 2007 Jan 9;. PMID:17213187

Page seeded by OCA on Wed Nov 21 13:15:52 2007