PDBsum entry 1hq2

Transferase

PDB id: 1hq2

Contents

Protein chain

158 a.a. *

Ligands

ACT ×4

APC

PH2

Metals

_MG ×2

_CL

Waters ×333

* Residue conservation analysis

References listed in PDB file

Key reference

• Title: Dynamic roles of arginine residues 82 and 92 of escherichia coli 6-Hydroxymethyl-7,8-Dihydropterin pyrophosphokinase: crystallographic studies.
• Authors: J.Blaszczyk, Y.Li, G.Shi, H.Yan, X.Ji.
• Ref.: Biochemistry, 2003, 42, 1573-1580. [DOI no: 10.1021/bi0267994]
• PubMed id: 12578370

Abstract

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.

Secondary reference #1

• Title: Crystal structure of 6-Hydroxymethyl-7,8-Dihydropterin pyrophosphokinase, A potential target for the development of novel antimicrobial agents.
• Authors: B.Xiao, G.Shi, X.Chen, H.Yan, X.Ji.
• Ref.: Structure, 1999, 7, 489-496. [DOI no: 10.1016/S0969-2126(99)80065-3]
• PubMed id: 10378268

Figure 1.
Figure 1. The folate biosynthetic pathway. The abbreviations for the enzymes of the pathway are given: HPPK, 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase; DHPS, dihydropteroate synthase; DHFS, dihydrofolate synthase; and DHFR, dihydrofolate reductase.

The above figure is reproduced from the cited reference with permission from Cell Press

Secondary reference #2

• Title: Catalytic center assembly of hppk as revealed by the crystal structure of a ternary complex at 1.25 a resolution.
• Authors: J.Blaszczyk, G.Shi, H.Yan, X.Ji.
• Ref.: Structure, 2000, 8, 1049-1058. [DOI no: 10.1016/S0969-2126(00)00502-5]
• PubMed id: 11080626

Figure 4.
Figure 4. The Open and Closed Catalytic Center of HPPK(a) The three uncoupled flexible loops of HPPK in the apo-enzyme [2].(b) The coupling of these loops in the ternary complex. In the ternary complex, a hydrogen-bond network involves N10 from Loop-1; P47 and Q50 from Loop-2; and W89, P91, and R92 from Loop-3. This network is not observed in apo-HPPK. The orientation of the drawing is indicated by the position of the substrate molecules HP and MgAMPCPP. (This figure was prepared with the program MOLSCRIPT [21].)

The above figure is reproduced from the cited reference with permission from Cell Press