1shn

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Revision as of 22:23, 24 November 2007

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spinqualitylabelsall models 1shn, resolution 2.15Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal structure of shrimp alkaline phosphatase with phosphate bound

Overview

Alkaline phosphatases (APs) are homodimeric metalloenzymes that catalyze, the hydrolysis and transphosphorylation of phosphate monoesters. Each, monomer contains a metal-binding triad that for optimal activity is, usually occupied by two zinc ions and one magnesium ion. The recently, determined crystal structure of cold-active shrimp alkaline phosphatase, (SAP) was, however, fully occupied by zinc ions. This paper describes a, metal-exchange experiment in which the zinc ion in one binding site, (referred to as the M3 site) is replaced by magnesium. Crystal structures, revealed a concomitant structural change: the metal exchange causes, movement of a ligating histidine into a conformation in which it does not, coordinate to the metal ion. The M3 site is relevant to catalysis: its, occupation by magnesium is postulated to favour catalysis and it has been, suggested to be a regulatory site for other APs. Further crystallographic, studies show that ligand binding can induce a conformational change of an, active-site arginine from a 'non-docked' (non-interacting) to a 'docked', conformation (interacting with the ligand). The first conformation has, only been observed in SAP, while the latter is common in available AP, structures. The observation that the arginine does not always bind the, substrate may explain the increased catalytic efficiency that is generally, observed for cold-active enzymes.

About this Structure

1SHN is a Single protein structure of sequence from Pandalus borealis with NAG, ZN, PO4 and SO4 as ligands. Active as Alkaline phosphatase, with EC number 3.1.3.1 Full crystallographic information is available from OCA.

Reference

Ligand-binding and metal-exchange crystallographic studies on shrimp alkaline phosphatase., de Backer MM, McSweeney S, Lindley PF, Hough E, Acta Crystallogr D Biol Crystallogr. 2004 Sep;60(Pt 9):1555-61. Epub 2004, Aug 26. PMID:15333925

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