1brw

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spinqualitylabelsall models 1brw, resolution 2.1Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

THE CRYSTAL STRUCTURE OF PYRIMIDINE NUCLEOSIDE PHOSPHORYLASE IN A CLOSED CONFORMATION

Overview

BACKGROUND: Pyrimidine nucleoside phosphorylase (PYNP) catalyzes the, reversible phosphorolysis of pyrimidines in the nucleotide synthesis, salvage pathway. In lower organisms (e.g. Bacillus stearothermophilus), PYNP accepts both thymidine and uridine, whereas in mammalian and other, higher organisms it is specific for thymidine (designated thymidine, phosphorylase, TP). PYNP shares 40% sequence similarity (and presumably, significant structural similarity) with human TP, which has been, implicated as a growth factor in tumor angiogenesis. It is thought that TP, undergoes a major conformational change upon substrate binding that, consequently produces an active conformation. RESULTS: The crystal, structure of PYNP from B. stearothermophilus with the substrate analog, pseudouridine in its active site has been solved to 2.1 A resolution. This, structure confirms the similarity of PYNP to TP and supports the idea of a, closed active conformation, which is the result of rigid body movement of, the alpha and alpha/beta domains. The active-site cleft, where the, pyrimidine and phosphate substrates bind, is between the two domains. The, structure reveals an asymmetric dimer in which one subunit is fully closed, and the other is only partially closed. CONCLUSIONS: The closed, conformation of PYNP serves as a good model to better understand the, domain movement and overall function of TP. Active-site residues are, confirmed and a possible mechanism for substrate binding and subsequent, domain movement is suggested. Potent inhibitors of TP might have, significant therapeutic value in various chemotherapeutic strategies, and, the structure of PYNP should provide valuable insight into the rational, design of such inhibitors.

About this Structure

1BRW is a Single protein structure of sequence from Geobacillus stearothermophilus with PO4, CA, URA and MES as ligands. Active as Pyrimidine-nucleoside phosphorylase, with EC number 2.4.2.2 Full crystallographic information is available from OCA.

Reference

The crystal structure of pyrimidine nucleoside phosphorylase in a closed conformation., Pugmire MJ, Ealick SE, Structure. 1998 Nov 15;6(11):1467-79. PMID:9817849

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