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compared with short-peptide-carrying ribosomes.

The chemical structure of lincomycin, clindamycin and celesticetin, like that of chloramphenicol, shows the presence of an amide bond and a group simulating the peptide group adjacent to the Ca-atom of the amino acid residue (here, again, the alcohol hydroxyl group is present instead of the acidic one). Mode of action of lincomycin and its derivatives seems to be similar to that of chloramphenicol, though there are indications that both a and p sites of PTC may be affected by the more massive antibiotics. The positions of mutations in 23 S RNA which confer the resistance against lincoasamides are G2032, G2057, A2058, and A2059, thus being near or within the PTC ring and overlapping with the positions of chloramphenicol resistance mutations. When bound, they protect residues A2058, A2059, and G2061 in the same region, as well as A2451 and G2505 in another region of chloramphenicol resistance mutations, also in PTC ring (Fig. 9.7).

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