2nra

From Proteopedia

Revision as of 10:44, 21 November 2007

Crystal structure of Pi initiator protein in complex with iteron DNA

Overview

We have determined the crystal structure of a monomeric biologically, active form of the pi initiator protein of plasmid R6K as a complex with a, single copy of its cognate DNA-binding site (iteron) at 3.1-A resolution., The initiator belongs to the family of winged helix type of proteins. The, structure reveals that the protein contacts the iteron DNA at two primary, recognition helices, namely the C-terminal alpha4' and the N-terminal, alpha4 helices, that recognize the 5' half and the 3' half of the 22-bp, iteron, respectively. The base-amino acid contacts are all located in, alpha4', whereas the alpha4 helix and its vicinity mainly contact the, phosphate groups of the iteron. Mutational analyses show that the contacts, of both recognition helices with DNA are necessary for iteron binding and, replication initiation. Considerations of a large number of site-directed, mutations reveal that two distinct regions, namely alpha2 and alpha5 and, its vicinity, are required for DNA looping and initiator dimerization, respectively. Further analysis of mutant forms of pi revealed the possible, domain that interacts with the DnaB helicase. Thus, the structure-function, analysis presented illuminates aspects of initiation mechanism of R6K and, its control.

About this Structure

2NRA is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

Crystal structure of pi initiator protein-iteron complex of plasmid R6K: implications for initiation of plasmid DNA replication., Swan MK, Bastia D, Davies C, Proc Natl Acad Sci U S A. 2006 Dec 5;103(49):18481-6. Epub 2006 Nov 21. PMID:17124167

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