1hq2

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spinqualitylabelsall models 1hq2, resolution 1.25Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

CRYSTAL STRUCTURE OF A TERNARY COMPLEX OF E.COLI HPPK(R82A) WITH MGAMPCPP AND 6-HYDROXYMETHYL-7,8-DIHYDROPTERIN AT 1.25 ANGSTROM RESOLUTION

Overview

6-Hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) catalyzes the, pyrophosphoryl transfer from ATP to 6-hydroxymethyl-7,8-dihydropterin, (HP), the first reaction in the folate biosynthetic pathway. Arginine, residues 82 and 92, strictly conserved in 35 HPPK sequences, play dynamic, roles in the catalytic cycle of the enzyme. At 0.89-A resolution, two, distinct conformations are observed for each of the two residues in the, crystal structure of the wild-type HPPK in complex with two HP variants, two Mg(2+) ions, and an ATP analogue. Structural information suggests that, R92 first binds to the alpha-phosphate group of ATP and then shifts to, interact with the beta-phosphate as R82, which initially does not bind to, ATP, moves in and binds to alpha-phosphate when the pyrophosphoryl, transfer is about to occur. The dynamic roles of R82 and R92 are further, elucidated by five more crystal structures of two mutant proteins, R82A, and R92A, with and without bound ligands. Two oxidized forms of HP are, observed with an occupancy ratio of 0.50:0.50 in the 0.89-A structure. The, oxidation of HP has significant impact on its binding to the protein as, well as the conformation of nearby residue W89.

About this Structure

1HQ2 is a Single protein structure of sequence from Escherichia coli with MG, CL, ACT, APC and PH2 as ligands. Active as 2-amino-4-hydroxy-6-hydroxymethyldihydropteridine diphosphokinase, with EC number 2.7.6.3 Full crystallographic information is available from OCA.

Reference

Dynamic roles of arginine residues 82 and 92 of Escherichia coli 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase: crystallographic studies., Blaszczyk J, Li Y, Shi G, Yan H, Ji X, Biochemistry. 2003 Feb 18;42(6):1573-80. PMID:12578370

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