Characterisation of the MutS and MutL Proteins from the Pseudomonas avellanae Mismatch Repair (MMR) System.

The identification and analysis of the Pseudomonas avellanae mismatch repair system (MMR) were performed via sequencing and cloning the mutS and mutL genes and then analyzing the characteristics of the corresponding proteins studying their function and biological role in an E. coli heterologous system. In these studies, the P. avellanae MutS and MutL proteins were shown to localise at the nucleoid level, in a MutS-dependent manner as far as MutL is concerned, and were also able to complement the defect observed in both the mutS and mutL knockout strains of E. coli. In addition, their ability to form both homo and heterodimers between each other was shown by using the prokaryotic two-hybrid assay. Our results represent a first step to elucidate the MMR mechanism in plant pathogenic pseudomonads since the MMR genes were identified in P. syringae pathovars but there was no evidence on their action as effective repair products.