Published online 14 March 2005
Article |
Dimeric configuration of SeqA protein bound to a pair of hemi-methylated GATC sequences
1Institute of Molecular Biology and Genetics, Seoul National University Seoul 151-742, Republic of Korea 2School of Biological Sciences, Seoul National University Seoul 151-742, Republic of Korea
*To whom correspondence should be addressed. Tel: +82 2 880 7524; Fax: +82 2 874 1206; Email: dshwang{at}plaza.snu.ac.kr
Received December 19, 2004. Revised February 18, 2005. Accepted February 18, 2005.
The binding of SeqA protein to hemi-methylated GATC sequences (hemi-sites) regulates chromosome initiation and the segregation of replicated chromosome in Escherichia coli. We have used atomic force microscopy to examine the architecture of SeqA and the mode of binding of one molecule of SeqA to a pair of hemi-sites in aqueous solution. SeqA has a bipartite structure composed of a large and a small lobe. Upon binding of a SeqA molecule to a pair of hemi-sites, the larger lobe becomes visibly separated into two DNA binding domains, each of which binds to one hemi-site. The two DNA binding domains are held together by association between the two multimerization domains that make up the smaller lobe. The binding of each DNA binding domain to a hemi-site leads to bending of the bound DNA inwards toward the bound protein. In this way, SeqA adopts a dimeric configuration when bound to a pair of hemi-sites. Mutational analysis of the multimerization domain indicates that, in addition to multimerization of SeqA polypeptides, this domain contributes to the ability of SeqA to bind to a pair of hemi-sites and to its cooperative behavior.
The authors wish it to be known that, in their opinion, the first three authors should be regarded as joint First Authors
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