The overall goal is to understand the structural basis of sequence recognition by DNA binding proteins. These studies have centered on the type II restriction-modification systems of bacteria, and in particular on the Pvu II system that was previously cloned from Proteus vulgaris. Four proteins that recognize the same DNA sequence which includes the Pvu II proteins will be characterized and compared. This comparison will be both structural and functional, and is intended to indicate the extent to which functionally-related proteins recognizing a common base sequences show structural homologies. The recognition of specific DNA sequences by proteins is so crucial to so many cellular processes that no mature understanding of cell physiology will be possible without understanding the basis of this recognition. These processes include promoter selection by RNA polymerases, the action of repressors, activators, enhancer-modulation, genetic recombination and transposition, and targeted DNA repair. Dr. Blumenthal is well trained for the work described here.