Johnston Danielle, Tavano Christine, Wickner Sue, Trun Nancy
Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282, USA.
J Biol Chem. 2006 Dec 29;281(52):40208-15. doi: 10.1074/jbc.M606414200. Epub 2006 Nov 4.
The CspE protein from Escherichia coli K12 is a single-stranded nucleic acid-binding protein that plays a role in chromosome condensation in vivo. We report here that CspE binds to single-stranded DNA containing 6 or more contiguous dT residues with high affinity (K(D) < 30 nM). The interactions are predominantly through base-specific contacts. When an oligonucleotide contains fewer than 6 contiguous dT residues, the CspE interactions with single-stranded DNA are primarily electrostatic. The minimal length of single-stranded DNA to which CspE binds in a salt-resistant manner is eight nucleotides. We also show that CspE exists as a dimer in solution. We present a possible mechanism to explain the role of CspE in chromosome condensation in vivo by CspE binding to distant DNA regions in the chromosome and dimerizing, thereby condensing the intervening DNA.
来自大肠杆菌K12的CspE蛋白是一种单链核酸结合蛋白，在体内染色体浓缩过程中发挥作用。我们在此报告，CspE以高亲和力（K(D) < 30 nM）结合含有6个或更多连续dT残基的单链DNA。这些相互作用主要通过碱基特异性接触。当寡核苷酸包含少于6个连续dT残基时，CspE与单链DNA的相互作用主要是静电作用。CspE以抗盐方式结合的单链DNA的最小长度为8个核苷酸。我们还表明，CspE在溶液中以二聚体形式存在。我们提出了一种可能的机制来解释CspE在体内染色体浓缩中的作用，即CspE与染色体中远距离的DNA区域结合并二聚化，从而浓缩中间的DNA。
