ANALISIS OF C-TERMINAL DELETED VERSIONS OF Escherichia coli MutS

MIGUEL, VIRGINIA; ; PEZZA, ROBERTO J. ; ARGARAÑA CARLOS E.

Pinamar, Argentina

Congreso; XLI Reunión Anual de SAIB; 2005

Mismatch Repair System (MMRS) contributes to genetic stability by correcting point mutations or small insertion/deletion loops. In addition, this system prevents recombination between partially homologous DNA sequences. In Escherichia coli, the assembly of the MMRS is initiated by MutS, an 853 amino acids protein which recognizes and binds to mispaired nucleotides. In vitro, MutS exists as dimers and tetramers in equilibrium. Deletion of the 53 C-terminal amino acids shifts the equilibrium to the tetramer form and avoids high order aggregate formation. The 53 C-terminal amino acids are essential for MutS function in-vivo. These results suggest that oligomerization state is a key process to MutS activity. In order to determine the role of the C-terminal portion on the oligomerization and stability of the protein, we have constructed three C-terminal deletion mutants of E. coli MutS. We characterized their biochemical activity and capacity to oligomerize and found that the deletion of just 7 amino acids (delta-848 mutant) resulted in the loss of tetramerization and high order aggregate formation. However, delta-848 retained its ATPase activity and DNA binding capability. All C-terminal deletion versions were able to partially complement an E. coli mutS deficient strain suggesting that they are very likely competent for mismatch repair.