GROWTH-PHASE AND GROWTH-RATE DEPENDENCE OF RIBOSOMAL PEPTIDYLTRANSFERASE ACTIVITY STATUS IN ESCHERICHIA-COLI

Ribosomes from a clinical isolate of E coli were purified and characte rized, The structural features of these ribosomes were identical to wi ld-type E coli ribosomes, with the exception that rRNA in general, bur especially 23S rRNA, was degraded as a result of the transition from early to late logarithmic growth phase, on different growth media. Ana lysis of the ribosomal protein by gel electrophoresis indicated that t he L12/L7 molar ratio increases during early logarithmic phase, reachi ng a maximum value of about 1.6 at midlogarithmic phase, and then fall ing to 0.7 in late logarithmic phase. Concomitantly with L12/L7 altera tions, the activity status of ribosomal peptidyltransferase was found to undergo a striking shift. Reconstitution experiments demonstrated t hat the two effects are closely related. Moreover, L12/L7 molar ratio as well as peptidyltransferase activity increased with increasing grow th rate. In the latter case, however, the acetylation level of L12 pro tein per se seemed to be inadequate to modulate the peptidyltransferas e activity.