THE ROLE OF THE PRESERVED SEQUENCES OF DAM METHYLASE

We have undertaken a site directed mutational analysis of two of the p reserved regions in the amino acid sequence of Dam methylase in order to characterize their role. Mutations in region IV (sequence DPPY) abo lish catalytic activity and greatly affect AdoMet crosslinking. Mutant s in region III display a lowered specific activity with an unchanged AdoMet crosslinking capacity. We have also made a series of deletions both at the N and C terminal parts of the protein, which have been fou nd to provide inactive enzyme. We discuss the significance of these re sults for the understanding of the functional properties of the enzyme .