Wang L, Voloshin O N, Stasiak A, Camerini-Otero R D
Rm 9D20, National Institutes of Health, Bethesda, MD 20892, USA.
J Mol Biol. 1998 Mar 20;277(1):1-11. doi: 10.1006/jmbi.1997.1591.
The 20 amino acid residue peptides derived from RecA loop L2 have been shown to be the pairing domain of RecA. The peptides bind to ss- and dsDNA, unstack ssDNA, and pair the ssDNA to its homologous target in a duplex DNA. As shown by circular dichroism, upon binding to DNA the disordered peptides adopt a beta-structure conformation. Here we show that the conformational change of the peptide from random coil to beta-structure is important in binding ss- and dsDNA. The beta-structure in the DNA pairing peptides can be induced by many environmental conditions such as high pH, high concentration, and non-micellar sodium dodecyl sulfate (6 mM). This behavior indicates an intrinsic property of these peptides to form a beta-structure. A beta-structure model for the loop L2 of RecA protein when bound to DNA is thus proposed. The fact that aromatic residues at the central position 203 strongly modulate the peptide binding to DNA and subsequent biochemical activities can be accounted for by the direct effect of the aromatic amino acids on the peptide conformational change. The DNA-pairing domain of RecA visualized by electron microscopy self-assembles into a filamentous structure like RecA. The relevance of such a peptide filamentous structure to the structure of RecA when bound to DNA is discussed.
源自RecA环L2的20个氨基酸残基的肽已被证明是RecA的配对结构域。这些肽与单链和双链DNA结合，解开单链DNA的堆积，并将单链DNA与其双链DNA中的同源靶标配对。圆二色性显示，与DNA结合后，无序的肽会呈现β结构构象。在这里，我们表明肽从无规卷曲到β结构的构象变化在结合单链和双链DNA中很重要。DNA配对肽中的β结构可以由许多环境条件诱导，如高pH、高浓度和非胶束十二烷基硫酸钠（6 mM）。这种行为表明这些肽具有形成β结构的内在特性。因此，提出了RecA蛋白环L2与DNA结合时的β结构模型。中心位置203处的芳香族残基强烈调节肽与DNA的结合以及随后的生化活性，这一事实可以通过芳香族氨基酸对肽构象变化的直接影响来解释。通过电子显微镜观察到的RecA的DNA配对结构域自组装成类似RecA的丝状结构。讨论了这种肽丝状结构与RecA与DNA结合时的结构的相关性。
