Effect of lincomycin and clindamycin on peptide chain initiation

Lincomycin does not affect initiation factor-dependent formation of 70S initiation complexes formed with fmet-tRNA(F), the initiation triplet A-U-G, and 70S ribosomes, whereas its 7-chloro-derivative clindamycin substantially stimulates this process. Conversely, lincomycin stimulates nonenzymatic formation of the 70S complex, but clindamycin does not. Both antibiotics stimulate the assembly of non-enzymatically formed 70S initiation complexes with R(17) phage ribonucleic acid and exert little effect on those formed in the presence of initiation factors. The formation of 30S initiation complexes is stimulated or remains unaffected by lincomycin or clindamycin except when initiation occurs in the presence of very low Mg(2+) concentrations. In this case, both antibiotics inhibit the assembly of the 30S complexes regardless of the messenger present.