1Z84

X-ray structure of galt-like protein from arabidopsis thaliana at5g18200

Summary for 1Z84

• Entry DOI: 10.2210/pdb1z84/pdb
• Related: 1ZWJ 2GDK
• Descriptor: galactose-1-phosphate uridyl transferase-like protein, ZINC ION, ADENOSINE MONOPHOSPHATE, ... (5 entities in total)
• Functional Keywords: galt, zinc, amp, structural genomics, protein structure initiative, psi, cesg, center for eukaryotic structural genomics, unknown function
• Biological source: Arabidopsis thaliana (thale cress)
• Total number of polymer chains: 2
• Total formula weight: 79434.80

Authors

Mccoy, J.G.,Bitto, E.,Phillips Jr., G.N.,Bingman, C.A.,Center for Eukaryotic Structural Genomics (CESG) (deposition date: 2005-03-29, release date: 2005-04-19, Last modification date: 2024-10-16)

Primary citation

MCCOY, J.G.,ARABSHAHI, A.,BITTO, E.,BINGMAN, C.A.,RUZICKA, F.J.,FREY, P.A.,PHILLIPS JR., G.N.
Structure and Mechanism of an ADP-Glucose Phosphorylase from Arabidopsis thaliana
Biochemistry, 45:3154-3162, 2006

PubMed Abstract: 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).

PubMed: 16519510
DOI: 10.1021/bi052232m

Experimental method

X-RAY DIFFRACTION (1.83 Å)