Structural and functional analysis of the C-terminal region of the P. aeruginosa MutS

MIGUEL VIRGINIA; MONTI MARIELA R.; ARGARAÑA CARLOS E.

Mar del Plata-Argentina

Congreso; XLIII Reunión Anual de SAIB; 2007

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Escherichia coli MutS, an 853 amino acids (aa) protein, is involved in the postreplicative DNA mismatch repair system (MMRS). This is an oligomeric protein with ATPase activity and capacity to bind to heteroduplex DNA. It is known that the E. coli MutS exists as dimers and tetramers and that the 53 C-terminal aa are responsible for oligomerization. We show that in vitro, Pseudomonas aeruginosa (PA) MutS also forms dimers and tetramers. Analysis of different C-terminal deletions and point mutations versions of MutS, and peptides fused to the monomeric maltose binding protein, indicate that the C-terminal region also drives the oligomerization process. Using E. coli and PA mutS deletion strains, we tested the capacity of different plasmid expressing C-terminal mutated versions of E. coli and PA MutS to restore MMRS functionality, by measuring the frequency of cells resistant to antibiotics. We found that E. coli and PA MutS point mutants with tetramerization defects, were complementation proficient; however the 53 C-terminal aa deleted version was able to complement E. coli but not PA. Western blot analysis indicates that this difference cannot be attributed to different expression levels of the protein. We conclude that although the tetramer specie of MutS may be dispensable, the C-terminal region is important for the functioning of the MMRS in PA.