单个RecA-DNA细丝的聚合作用及机械性能
Polymerization and mechanical properties of single RecA-DNA filaments.
作者信息
Hegner M, Smith S B, Bustamante C
机构信息
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
出版信息
Proc Natl Acad Sci U S A. 1999 Aug 31;96(18):10109-14. doi: 10.1073/pnas.96.18.10109.
The polymerization of individual RecA-DNA filaments, containing either single-stranded or double-stranded DNA, was followed in real time, and their mechanical properties were characterized with force-measuring laser tweezers. It was found that the stretch modulus of a filament is dominated by its (central) DNA component, while its bending rigidity is controlled by its (eccentric) protein component. The longitudinal stiffness of DNA increases 6- to 12-fold when the DNA is contained in the protein helix. Both the stretch modulus and the bending rigidity of a fiber change in the presence of various nucleotide cofactors-e.g., [gamma-thio]ATP, ATP, and ADP-indicating a substantial re-arrangement of spatial relationships between the nucleic acid and the protein scaffold. In particular, when complexed with ATP, a fiber becomes twice as extensible as a [gamma-thio]ATP fiber, suggesting that 32% of the DNA-binding sites have been released in its core. Such release may enable easy rotation of the DNA within the protein helix or slippage of the DNA through the center of the protein helix.
实时跟踪了含有单链或双链DNA的单个RecA-DNA细丝的聚合过程，并用测力激光镊子对其力学性质进行了表征。结果发现，细丝的拉伸模量主要由其（中心）DNA成分决定，而其弯曲刚度则由其（偏心）蛋白质成分控制。当DNA包含在蛋白质螺旋中时，DNA的纵向刚度增加6至12倍。在各种核苷酸辅因子（例如，[γ-硫代]ATP、ATP和ADP）存在的情况下，纤维的拉伸模量和弯曲刚度都会发生变化，这表明核酸与蛋白质支架之间的空间关系发生了实质性的重新排列。特别是，当与ATP结合时，纤维的可伸展性是[γ-硫代]ATP纤维的两倍，这表明其核心中32%的DNA结合位点已被释放。这种释放可能使DNA在蛋白质螺旋内易于旋转或通过蛋白质螺旋中心滑动。
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