The recombinases present in the all kingdoms in nature play a crucial role in DNA metabolism processes such as replication, repair, recombination and transcription. However, till date, the role of RecA in the deadly foodborne pathogen Listeria monocytogenes remains unknown. In this study, the authors show that L. monocytogenes expresses recA more than two-fold in vivo upon exposure to the DNA damaging agents, methyl methanesulfonate and ultraviolet radiation. The purified L. monocytogenes RecA protein show robust binding to single stranded DNA. The RecA is capable of forming displacement loop and hydrolyzes ATP, whereas the mutant LmRecA^K70A fails to hydrolyze ATP, showing conserved walker A and B motifs. Interestingly, L. monocytogenes RecA and LmRecA^K70A perform the DNA strand transfer activity, which is the hallmark feature of RecA protein with an oligonucleotide-based substrate. Notably, L. monocytogenes RecA readily cleaves L. monocytogenes LexA, the SOS regulon and protects the presynaptic filament from the exonuclease I activity. Altogether, this study provides the first detailed characterization of L. monocytogenes RecA and presents important insights into the process of homologous recombination in the gram-positive foodborne bacteria L. monocytogenes.

自然界中所有王国中都存在的重组酶在DNA代谢过程（例如复制，修复，重组和转录）中起着至关重要的作用。然而，迄今为止，RecA在致命的食源性单核细胞增生李斯特氏菌中的作用仍然未知。在这项研究中，作者显示，大号。在暴露于DNA破坏剂，甲烷磺酸甲酯和紫外线照射下，单核细胞增生因子在体内表达recA的两倍以上。将纯化的大号。单核细胞增生因子RecA蛋白显示与单链DNA的牢固结合。RecA能够形成置换环并水解ATP，而突变型LmRecA ^K70A不能水解ATP，显示保守的助步器A和B图案。有趣的是，L。单核细胞增生因子RecA和LmRecA ^K70A具有DNA链转移活性，这是RecA蛋白与基于寡核苷酸的底物的标志性特征。显然，L。菌等的RecA容易裂解大号。单核细胞增生症LexA，SOS调节剂，保护突触前丝免受核酸外切酶I活性。总之，本研究提供了L的第一个详细表征。单核细胞增生RecA并提供了对革兰氏阳性食源性细菌L中同源重组过程的重要见解。单核细胞增生