Ali B M, Amit R, Braslavsky I, Oppenheim A B, Gileadi O, Stavans J
Department of Physics of Complex Systems, the Weizmann Institute of Science, Rehovot 76100, Israel.
Proc Natl Acad Sci U S A. 2001 Sep 11;98(19):10658-63. doi: 10.1073/pnas.181029198. Epub 2001 Sep 4.
We studied the interaction between the integration host factor (IHF), a major nucleoid-associated protein in bacteria, and single DNA molecules. Force-extension measurements of lambda DNA and an analysis of the Brownian motion of small beads tethered to a surface by single short DNA molecules, in equilibrium with an IHF solution, indicate that: (i) the DNA-IHF complex retains a random, although more compact, coiled configuration for zero or small values of the tension, (ii) IHF induces DNA compaction by binding to multiple DNA sites with low specificity, and (iii) with increasing tension on the DNA, the elastic properties of bare DNA are recovered. This behavior is consistent with the predictions of a statistical mechanical model describing how proteins bending DNA are driven off by an applied tension on the DNA molecule. Estimates of the amount of bound IHF in DNA-IHF complexes obtained from the model agree very well with independent measurements of this quantity obtained from the analysis of DNA-IHF crosslinking. Our findings support the long-held view that IHF and other histone-like proteins play an important role in shaping the long-scale structure of the bacterial nucleoid.
我们研究了细菌中主要的类核相关蛋白整合宿主因子（IHF）与单个DNA分子之间的相互作用。对λDNA进行的力-伸长测量以及对通过单个短DNA分子 tethered 到表面的小珠子的布朗运动分析，在与IHF溶液达到平衡时，表明：（i）对于零或小张力值，DNA-IHF复合物保持随机但更紧凑的盘绕构型；（ii）IHF通过以低特异性结合多个DNA位点诱导DNA压缩；（iii）随着DNA上张力的增加，裸露DNA的弹性特性得以恢复。这种行为与描述施加在DNA分子上的张力如何驱离使DNA弯曲的蛋白质的统计力学模型的预测一致。从该模型获得的DNA-IHF复合物中结合的IHF量的估计值与通过DNA-IHF交联分析独立测量的该量非常吻合。我们的研究结果支持长期以来的观点，即IHF和其他组蛋白样蛋白在塑造细菌类核的长尺度结构中起重要作用。 （注：tethered这个词在原文中可能有误，推测可能是“连接”之类的意思，这里按原文翻译）
