Two-dimensional electrophoretic analysis of the regulation of SOS proteins in three ssb mutants

A previously undescribed mutation in the ssb gene, which codes for a major single strand DNA binding protein essential for DNA repelication, was mapped on the Escherichia coli Chromosome. Three ssb mutants were analyzed under parallel physiological conditions for the induction of SOS proteins (products of recA, uvrA, and an unknown gene), the production of mutants, the induction of lambda prophage, and sensitivity to DNA damaging agents. Two-dimensional electrophoretic techniques were used to quantitate changes in the rate of synthesis of proteins. The previously unpublished position of the uvrA gene-product in the two-dimensional matrix of E. coli proteins was described. These ssb strains exhibited varying sensitivities to ultraviolet irradiation and methylmethane sulfonate that correlated with the rate of constitutive synthesis of SOS proteins, spontaneous commitment to virulent growth of lambda lysogens, and elevation of endogenous mutation rates.Dedicated to the memory of Roger Y. Stanier: to his fascination for diverse microbial lifeforms that catalyzed curiosity in his associates, to his intellectual aura that elicited deep respect, to his pursuit of scientific truth that promoted the highest research ethics, to his friendly nature that encouraged my growth as a scientist and enkindled my love for Roger