BACTERIAL PROTEASE LON IS A SITE-SPECIFIC DNA-BINDING PROTEIN

The product of the Escherichia coli lon gene is the ATP-dependent Lon protease, Lon contributes to the regulation of several important cellu lar functions, including radiation resistance, cell division, filament ation, capsular polysaccharide production, lysogeny of certain bacteri ophages, and proteolytic degradation of certain regulatory and abnorma l proteins, Lon homologues are also found in several widely divergent bacteria, as well as in the mitochondria of yeast and humans, E. coli Lon has long been known to bind to DNA, but this interaction has not b een further characterized and has generally been assumed to be nonspec ific, We now demonstrate that E. coli Lon can bind to a TG-rich DNA pr omoter element in a sequence specific manner, This finding is based on the results of experiments employing SouthWestern blotting, protein p urification, ''shift-shift'' electrophoretic mobility shift assays, el ectrophoretic mobility shift assays using in vitro transcribed and tra nslated Lon, and DNase footprinting, Site-specific DNA binding is like ly to be an additional important biochemical characteristic of the mul tifaceted Lon protease.