Liveris Dionysios, Mulay Vishwaroop, Schwartz Ira
Department of Microbiology & Immunology, New York Medical College, Valhalla, New York 10595, USA.
J Bacteriol. 2004 Apr;186(8):2275-80. doi: 10.1128/JB.186.8.2275-2280.2004.
Functions of the Borrelia burgdorferi RecA protein were investigated in Escherichia coli recA null mutants. Complementation with B. burgdorferi recA increased survival of E. coli recA mutants by 3 orders of magnitude at a UV dose of 2,000 microJ/cm(2). The viability at this UV dose was about 10% that provided by the homologous recA gene. Expression of B. burgdorferi recA resulted in survival of E. coli at levels of mitomycin C that were lethal to noncomplemented hosts. B. burgdorferi RecA was as effective as E. coli RecA in mediating homologous recombination in E. coli. Furthermore, E. coli lambda phage lysogens complemented with B. burgdorferi recA produced phage even in the absence of UV irradiation. The level of phage induction was 55-fold higher than the level in cells complemented with the homologous recA gene, suggesting that B. burgdorferi RecA may possess an enhanced coprotease activity. This study indicates that B. burgdorferi RecA mediates the same functions in E. coli as the homologous E. coli protein mediates. However, the rapid loss of viability and the absence of induction in recA expression after UV irradiation in B. burgdorferi suggest that recA is not involved in the repair of UV-induced damage in B. burgdorferi. The primary role of RecA in B. burgdorferi is likely to be a role in some aspect of recombination.
在大肠杆菌recA基因缺失突变体中研究了伯氏疏螺旋体RecA蛋白的功能。用伯氏疏螺旋体recA基因进行互补，可使大肠杆菌recA突变体在紫外线剂量为2000微焦/平方厘米时的存活率提高3个数量级。在此紫外线剂量下的存活率约为同源recA基因所提供存活率的10%。伯氏疏螺旋体recA基因的表达使大肠杆菌在丝裂霉素C水平下能够存活，而该水平对未互补的宿主是致死的。在介导大肠杆菌的同源重组方面，伯氏疏螺旋体RecA与大肠杆菌RecA一样有效。此外，用伯氏疏螺旋体recA基因互补的大肠杆菌λ噬菌体溶原菌即使在没有紫外线照射的情况下也能产生噬菌体。噬菌体诱导水平比用同源recA基因互补的细胞中的水平高55倍，这表明伯氏疏螺旋体RecA可能具有增强的共蛋白酶活性。这项研究表明，伯氏疏螺旋体RecA在大肠杆菌中发挥的功能与同源的大肠杆菌蛋白所介导的功能相同。然而，伯氏疏螺旋体在紫外线照射后存活率迅速丧失且recA表达没有诱导现象，这表明recA不参与伯氏疏螺旋体中紫外线诱导损伤的修复。RecA在伯氏疏螺旋体中的主要作用可能是在重组的某些方面发挥作用。
