枯草芽孢杆菌嘌呤阻遏物与DNA的相互作用。
Interaction of Bacillus subtilis purine repressor with DNA.
作者信息
Shin B S, Stein A, Zalkin H
机构信息
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907, USA.
出版信息
J Bacteriol. 1997 Dec;179(23):7394-402. doi: 10.1128/jb.179.23.7394-7402.1997.
A purine repressor (PurR) mediates adenine nucleotide-dependent regulation of transcription initiation of the Bacillus subtilis pur operon. This repressor has been purified for the first time, and binding to control site DNA was characterized. PurR binds in vitro to four operons. Apparent Kd values for binding were 7 nM for the pur operon, 8 nM for purA, 13 nM for purR, and 44 nM for the pyr operon. In each case, DNase I footprints exhibited a pattern of protected and hypersensitive sites that extended over more than 60 bp. A GAAC-N24-GTTC sequence in the pur operon was necessary but not sufficient for the PurR-DNA interaction. However, this motif, which is conserved in the four binding sites, was not required for binding of PurR to purA. Thus, the common DNA recognition element for binding of PurR to the four operons is not known. Multiple PurR-pur operon DNA complexes having a binding stoichiometry that was either approximately two or six repressor molecules per DNA fragment were detected. The results of a torsional constraint experiment suggest that control site DNA forms one right-handed turn around PurR.
嘌呤阻遏蛋白（PurR）介导枯草芽孢杆菌嘌呤操纵子转录起始的腺嘌呤核苷酸依赖性调控。该阻遏蛋白首次被纯化，并对其与控制位点DNA的结合进行了表征。PurR在体外与四个操纵子结合。结合的表观解离常数（Kd）值分别为：嘌呤操纵子7 nM、purA 8 nM、purR 13 nM、嘧啶操纵子44 nM。在每种情况下，DNA酶I足迹显示出延伸超过60 bp的受保护和超敏位点模式。嘌呤操纵子中的GAAC-N24-GTTC序列对于PurR与DNA的相互作用是必要的，但并不充分。然而，在四个结合位点中保守的这个基序对于PurR与purA的结合并非必需。因此，PurR与四个操纵子结合的共同DNA识别元件尚不清楚。检测到多个PurR-嘌呤操纵子DNA复合物，其结合化学计量约为每个DNA片段两个或六个阻遏蛋白分子。扭转约束实验结果表明，控制位点DNA围绕PurR形成一个右手螺旋。
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