PDBsum entry 1ex8

Transferase

PDB id: 1ex8

Contents

Protein chain

158 a.a. *

Ligands

A4P

Metals

_MG

_CL

Waters ×167

* Residue conservation analysis

References listed in PDB file

Key reference

• Title: Bisubstrate analogue inhibitors of 6-Hydroxymethyl-7,8-Dihydropterin pyrophosphokinase: synthesis and biochemical and crystallographic studies.
• Authors: G.Shi, J.Blaszczyk, X.Ji, H.Yan.
• Ref.: J Med Chem, 2001, 44, 1364-1371. [DOI no: 10.1021/jm0004493]
• PubMed id: 11311059

Abstract

6-Hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) catalyzes the transfer of pyrophosphate from ATP to 6-hydroxymethyl-7,8-dihydropterin (HP), leading to the biosynthesis of folate cofactors. Like other enzymes in the folate pathway, HPPK is an ideal target for the development of antimicrobial agents because the enzyme is essential for microorganisms but is absent from human and animals. Three bisubstrate analogues have been synthesized for HPPK and characterized by biochemical and X-ray crystallographic analyses. All three bisubstrate analogues consist of a pterin, an adenosine moiety, and a link composed of 2-4 phosphoryl groups. P(1)-(6-Hydroxymethylpterin)-P(2)-(5'-adenosyl)diphosphate (HP(2)A, 5) shows little affinity and inhibitory activity for E. coli HPPK. P(1)-(6-Hydroxymethylpterin)-P(3)-(5'-adenosyl)triphosphate (HP(3)A, 6) shows moderate affinity and inhibitory activity with K(d) = 4.25 microM in the presence of Mg(2+) and IC(50) = 1.27 microM. P(1)-(6-Hydroxymethylpterin)-P(4)-(5'-adenosyl)tetraphosphate (HP(4)A, 7) shows the highest affinity and inhibitory activity with K(d) = 0.47 microM in the presence of Mg(2+) and IC(50) = 0.44 microM. The affinity of MgHP(4)A for HPPK is approximately 116 and 76 times higher than that of MgADP and 6-hydroxymethylpterin, respectively. The crystal structure of HPPK in complex with 7 (HPPK.MgHP(4)A) has been determined at 1.85 A resolution with a crystallographic R factor of 0.185. The crystal structure shows that 7 occupies both HP- and ATP-binding sites and induces significant conformational changes in HPPK. The biochemical and structural studies of the bisubstrate analogues indicate that the bisubstrate analogue approach can produce more potent inhibitors for HPPK and the minimum length of the link for a bisubstrate analogue is approximately 7 A.

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