1vq2

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spinqualitylabelsall models 1vq2, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

CRYSTAL STRUCTURE OF T4-BACTERIOPHAGE DEOXYCYTIDYLATE DEAMINASE, MUTANT R115E

Overview

2'-Deoxycytidylate deaminase (dCD) converts deoxycytidine 5'-monophosphate, (dCMP) to deoxyuridine 5'-monophosphate and is a major supplier of the, substrate for thymidylate synthase, an important enzyme in DNA synthesis, and a major target for cancer chemotherapy. Wild-type dCD is, allosterically regulated by the end products of its metabolic pathway, deoxycytidine 5'-triphosphate and deoxythymidine 5'-triphosphate, which, act as an activator and an inhibitor, respectively. The first crystal, structure of a dCD, in the form of the R115E mutant of the, T4-bacteriophage enzyme complexed with the active site inhibitor, pyrimidin-2-one deoxyribotide, has been determined at 2.2 A resolution., This mutant of dCD is active, even in the absence of the allosteric, regulators. The molecular topology of dCD is related to that of cytidine, deaminase (CDA) but with modifications for formation of the binding site, for the phosphate group of dCMP. The enzyme has a zinc ion-based mechanism, that is similar to that of CDA. A second zinc ion that is present in, bacteriophage dCD, but absent in mammalian dCD and CDA, is important for, the structural integrity of the enzyme and for the binding of the, phosphate group of the substrate or inhibitor. Although the R115E mutant, of dCD is a dimer in solution, it crystallizes as a hexamer, mimicking the, natural state of the wild-type enzyme. Residues 112 and 115, which are, known to be important for the binding of the allosteric regulators, are, found in a pocket that is at the intersubunit interfaces in the hexamer, but distant from the substrate-binding site. The substrate-binding site is, composed of residues from a single protein molecule and is sequestered in, a deep groove. This groove is located at the outer surface of the hexamer, but ends at the subunit interface that also includes residue 115. It is, proposed that the absence of subunit interactions at this interface in the, dimeric R115E mutant renders the substrate-binding site accessible. In, contrast, for the wild-type enzyme, binding of dCTP induces an allosteric, effect that affects the subunit interactions and results in an increase in, the accessibility of the binding site.

About this Structure

1VQ2 is a Single protein structure of sequence from Bacteriophage t4 with ZN and DDN as ligands. This structure superseeds the now removed PDB entry 1TEO. Active as dCMP deaminase, with EC number 3.5.4.12 Full crystallographic information is available from OCA.

Reference

Three-dimensional structure of the R115E mutant of T4-bacteriophage 2'-deoxycytidylate deaminase., Almog R, Maley F, Maley GF, Maccoll R, Van Roey P, Biochemistry. 2004 Nov 2;43(43):13715-23. PMID:15504034

Page seeded by OCA on Wed Nov 21 05:00:15 2007