Rate, accuracy and cost of ribosomes in bacterial cells

Abstract

Recent biochemical data on the rate of peptidyl-transfer and missense error levels associated with the E. coli ribosome in conjunction with direct measurements of diffusion constants for proteins in the E. coli cell have been used to discuss protein synthesis in the living E. coli cell in the perspective of a previously developed maximal fitness theory. With these improved experimental parameters, i.e. kcat approximately 50 s(-1) for protein elongation and kcat/KM approximately 4 microM(-1) s(-1) for cognate ternary complex binding to the ribosomal A site, theory predicts the experimentally observed variations in protein elongation rate, ribosome and ternary complex concentrations with varying quality of the growth medium. The theoretically predicted average missense error level is close the error levels estimated in vitro for special isoacceptor combinations, i.e. error levels about 1 per million. The future prospect of extensive integration of biochemistry, cell physiology and population genetics is discussed in the light of the maximal fitness theory and other, similar, theoretical approaches.