1zwj

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spinqualitylabelsall models 1zwj, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

X-ray structure of galt-like protein from arabidopsis thaliana AT5G18200

Overview

The X-ray crystal structure of the At5g18200.1 protein has been determined, to a nominal resolution of 2.30 A. The structure has a histidine triad, (HIT)-like fold containing two distinct HIT-like motifs. The sequence of, At5g18200.1 indicates a distant family relationship to the Escherichia, coli galactose-1-P uridylyltransferase (GalT): the determined structure of, the At5g18200.1 protein confirms this relationship. The At5g18200.1, protein does not demonstrate GalT activity but instead catalyzes adenylyl, transfer in the reaction of ADP-glucose with various phosphates. The best, acceptor among those evaluated is phosphate itself; thus, the At5g18200.1, enzyme appears to be an ADP-glucose phosphorylase. The enzyme catalyzes, the exchange of (14)C between ADP-[(14)C]glucose and glucose-1-P in the, absence of phosphate. The steady state kinetics of exchange follows the, ping-pong bi-bi kinetic mechanism, with a k(cat) of 4.1 s(-)(1) and K(m), values of 1.4 and 83 microM for ADP-[(14)C]glucose and glucose-1-P, respectively, at pH 8.5 and 25 degrees C. The overall reaction of, ADP-glucose with phosphate to produce ADP and glucose-1-P follows, ping-pong bi-bi steady state kinetics, with a k(cat) of 2.7 s(-)(1) and, K(m) values of 6.9 and 90 microM for ADP-glucose and phosphate, respectively, at pH 8.5 and 25 degrees C. The kinetics are consistent with, a double-displacement mechanism that involves a covalent adenylyl-enzyme, intermediate. The X-ray crystal structure of this intermediate was, determined to 1.83 A resolution and shows the AMP group bonded to, His(186). The value of K(eq) in the direction of ADP and glucose-1-P, formation is 5.0 at pH 7.0 and 25 degrees C in the absence of a divalent, metal ion, and it is 40 in the presence of 1 mM MgCl(2).

About this Structure

1ZWJ is a Single protein structure of sequence from Arabidopsis thaliana with ZN as ligand. This structure superseeds the now removed PDB entry 1VKV. Full crystallographic information is available from OCA.

Reference

Structure and mechanism of an ADP-glucose phosphorylase from Arabidopsis thaliana., McCoy JG, Arabshahi A, Bitto E, Bingman CA, Ruzicka FJ, Frey PA, Phillips GN Jr, Biochemistry. 2006 Mar 14;45(10):3154-62. PMID:16519510

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