Studies of the protein encoded by the lon mutation, capR9, in Escherichia coli. A labile form of the ATP-dependent protease La that inhibits the wild type protease.

摘要: The product of the lon (capR or deg) gene in Escherichia coli is protease La, an ATP-dependent with a linked ATPase activity. Unlike most mutations, capR9 dominant over wild type under certain conditions. When La was isolated from R9 cells and recessive capR- strain using DEAE-cellulose chromatography, mutant enzymes showed about 50% type, R- proteases were inhibited by addition NaCl (less than 0.1 M). In addition, R9, but not R-, material protelysis normal this effect may account for its phenotype. phosphocellulose protein lost proteolytic activity still enzyme. This inhibitory purified to near homogeneity heparin-agarose corresponded 94,000-dalton product. At different concentrations, it casein degradation casein-stimulated ATP hydrolysis similar extent. Thus, rates cleavage remained proportional. Similar inhibition observed presence DNA which stimulates both hydrolysis. Half-maximal approximately 1:1 ratio protein. subunit sizes indistinguishable they differed isoelectric points. Upon gel filtration, eluted as tetramers (450,000 daltons) absence salt. However, M NaCl, tetramer, dissociated into dimers monomers became more effective inhibitor. After mixing protein, 3H-labeled tetrameric, though had These findings suggest that tetramer formation between defective subunits responsible activities.