journals.plos.org
Species-specific coevolution of RecA–RecN interfaces governs DNA double-strand break repair in Escherichia coli
Author summary DNA double-strand breaks (DSBs) pose a serious threat to genomic integrity, and their accurate repair is essential for cell survival. In bacteria, DSB repair largely depends on homologous recombination mediated by the RecA recombinase and supported by the SMC-like protein RecN. Although RecA and RecN are known to cooperate, how their interaction contributes to efficient repair has remained unclear. Here, we investigated the functional relationship between RecA and RecN by expressing proteins from Pseudomonas aeruginosa in Escherichia coli. We found that P. aeruginosa RecN (paRecN) exhibits limited activity in E. coli but regains full functionality when co-expressed with its cognate RecA, revealing strong species-specific compatibility. Furthermore, we identified gain-of-function paRecN mutants that restore compatibility with E. coli RecA while losing compatibility with their native partner. These findings demonstrate that the RecA–RecN interaction interface is shaped by species-specific coevolution. Our study provides mechanistic and evolutionary insights into how protein–protein interactions involved in genome maintenance are optimized within each species.