The influence of growth phase and ionic environment on the dissociation of Escherichia coli ribosomes by p-chloromercuribenzoate

Abstract

The effect of p-chloromercuribenzoate (PCMB) on the structure of polysomes and ribosomes isolated from early log phase and stationary phase cells of Escherichia coli B has been studied in the presence and absence of K+. At 0° no breakdown of polysomes was observed in the presence of 0.5 mM PCMB. The 100S dimer, however, both at 0° and 25°, was readily dissociated under all conditions tested. The dissociation of 70S particles was much more sluggish and was most apparent in ribosomes isolated from early log phase cells in buffer containing K+. These results indicate that the sulfhydryl groups involved in 100S dissociation are more accessible to PCMB than those involved in the dissociation of 70S particles.