Crystal structure of deoxycytidylate hydroxymethylase from bacteriophage T4, a component of the deoxyribonucleoside triphosphate-synthesizing complex

被引:25
作者
Song, HK [1 ]
Sohn, SH [1 ]
Suh, SW [1 ]
机构
[1] Seoul Natl Univ, Coll Nat Sci, Dept Chem, Seoul 151742, South Korea
关键词
bacteriophage T4; deoxycytidylate hydroxymethylase deoxyuridylate hydroxymethylase; dNTP-synthesizing complex; thymidylate synthase;
D O I
10.1093/emboj/18.5.1104
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Bacteriophage T4 deoxycytidylate hydroxymethylase (EC 2,1,2,8), a homodimer of 246-residue subunits, catalyzes hydroxymethylation of the cytosine base in deoxycytidylate (dCMP) to produce 5-hydroxymethyl-dCMP. It forms part of a phage DNA protection system and appears to function iii vivo as a component of a multienzyme complex called deoxyribonucleoside triphosphate (dNTP) synthetase. We have determined its crystal structure in the presence of the substrate dCMP at 1.6 Angstrom resolution. The structure reveals a subunit fold and a dimerization pattern in common with thymidylate synthases, despite low (similar to 20%) sequence identity. Among the residues that form the dCMP binding site, those interacting with the sugar and phosphate are arranged in a configuration similar to the deoxyuridylate binding site of thymidylate synthases, However, the residues interacting directly or indirectly with the cytosine base show a more divergent structure and the presumed folate cofactor binding site is more open. Our structure reveals a water molecule properly positioned near C-6 of cytosine to add to the C-7 methylene intermediate during the last step of hydroxymethylation. On the basis of sequence comparison and crystal packing analysis, a hypothetical model for the interaction between T4 deoxycytidylate hydroxymethylase and T4 thymidylate synthase in the dNTP-synthesizing complex has been built.
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页码:1104 / 1113
页数:10
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