PHYSIOLOGICAL ROLE OF 70 <i>S</i> RIBOSOMES IN BACTERIA

Abstract

Evidence is presented indicating that free 70S ribosomes are real components of Bacillus stearothermophilus and Escherichia coli in exponential and stationary phases of growth. After pulses of radioactive leucine or uracil were given, protein synthesis was instantaneously stopped by chloramphenicol, or polypeptide growth was allowed to proceed to completion in slowly cooled cells. Analysis of label distribution in sucrose gradients showed that 70S monomers, and not subunits, are final products of translation.A ribosome cycle for protein synthesis in bacteria is proposed.