1wpk
From Proteopedia
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Methylated Form of N-terminal Transcriptional Regulator Domain of Escherichia Coli Ada Protein
Overview
The N-terminal 16-kDa domain of Escherichia coli Ada protein (N-Ada16k), repairs DNA methyl phosphotriester lesions by an irreversible methyl, transfer to its cysteine residue. Upon the methylation, the, sequence-specific DNA binding affinity for the promoter region of the, alkylation resistance genes is enhanced by 10(3)-fold. Then, it acts as a, transcriptional regulator for the methylation damage. In this paper, we, identified the methyl acceptor residue of N-Ada16k and determined the, solution structure of the methylated form of N-Ada16k by using NMR and, mass spectrometry. The results of a 13C-filtered 1H-13C HMBC experiment, and MALDI-TOF MS and MS/MS experiments clearly showed that the methyl, acceptor residue is Cys38. The solution structure revealed that it has two, distinct subdomains connected by a flexible linker loop: the, methyltransferase (MTase) subdomain with the zinc-thiolate center, and the, helical subdomain with a helix-turn-helix motif. Interestingly, there is, no potential hydrogen bond donor around Cys38, whereas the other three, cysteine residues coordinated to a zinc ion have potential donors. Hence, Cys38 could retain its inherent nucleophilicity and react with a methyl, phosphotriester. Furthermore, the structure comparison shows that there is, no indication of a remarkable conformational change occurring upon the, methylation. This implies that the electrostatic repulsion between the, negatively charged DNA and the zinc-thiolate center may avoid the contact, between the MTase subdomain and the DNA in the nonmethylated form. Thus, after the Cys38 methylation, the MTase subdomain can bind the cognate DNA, because the negative charge of the zinc-thiolate center is reduced.
About this Structure
1WPK is a Single protein structure of sequence from Escherichia coli with ZN as ligand. Full crystallographic information is available from OCA.
Reference
The solution structure of the methylated form of the N-terminal 16-kDa domain of Escherichia coli Ada protein., Takinowaki H, Matsuda Y, Yoshida T, Kobayashi Y, Ohkubo T, Protein Sci. 2006 Mar;15(3):487-97. Epub 2006 Feb 1. PMID:16452614
Page seeded by OCA on Wed Nov 21 05:34:59 2007
