Effect of lincomycin and clindamycin on peptide chain initiation.
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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. (+info)
Transduction of drug resistance to tetracycline, chloramphenicol, macrolides, lincomycin and clindamycin with phages induced from Streptococcus pyogenes.
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Strains of Streptococcus pyogenes isolated from pediatric patients with acute infections which were resistant to one or more of the antibiotics, tetracycline (TC), chloramphenicol (CP), macrolide antibiotics (erythromycin, kitasamycin, oleandomycin, josamycin), lincomycin (LCM) and clindamycin (CLM), were used for transduction of drug resistance. These drug-resistant strains were treated with mitomycin C to induce phages and transduction of drug resistance was attempted by means of phages so induced. It was found that transduction of resistance to the above antibiotics was possible. The transductants obtained on TC-containing selective agar plate were resistant to TC alone while those produced on CP- or erythromycin (EM)-containing selective agar plate were resistant to CP, macrolide antibiotics (Mac), LCM and CLM. From this finding, it was inferred that transduction of resistance to TC, CP, Mac, LCM and CLM via phages occurred in two different patterns, i.e., transfer of resistance to TC alone and that of resistance to CP, Mac, LCM and CLM. All of the transductants obtained were found to belong to group A. In T-typing, they were of the same T-12 type as the donor and recipient strains in a majority of cases though some were not typable. (+info)
Structural basis for selectivity and toxicity of ribosomal antibiotics.
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Ribosomal antibiotics must discriminate between bacterial and eukaryotic ribosomes to various extents. Despite major differences in bacterial and eukaryotic ribosome structure, a single nucleotide or amino acid determines the selectivity of drugs affecting protein synthesis. Analysis of resistance mutations in bacteria allows the prediction of whether cytoplasmic or mitochondrial ribosomes in eukaryotic cells will be sensitive to the drug. This has important implications for drug specificity and toxicity. Together with recent data on the structure of ribosomal subunits these data provide the basis for development of new ribosomal antibiotics by rationale drug design. (+info)
Susceptibility of various serogroups of streptococci to clindamycin and lincomycin.
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The minimal inhibitory concentration of lincomycin and clindamycin for a large number of strains from multiple serogroups of streptococci was determined. The median minimal inhibitory concentration for streptococci from groups A, B, C, F, G, H, L, and M and nongroupable organisms ranged from 0.02 to 0.39 mug of lincomycin per ml and from +info)
Spontaneous erythromycin resistance mutation in a 23S rRNA gene, rrlA, of the extreme thermophile Thermus thermophilus IB-21.
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Spontaneous, erythromycin-resistant mutants of Thermus thermophilus IB-21 were isolated and found to carry the mutation A2058G in one of two 23S rRNA operons. The heterozygosity of these mutants indicates that A2058G confers a dominant or codominant phenotype in this organism. This mutation provides a valuable tool for the genetic manipulation of the 23S rRNA genes of Thermus. (+info)
Gene lmrB of Corynebacterium glutamicum confers efflux-mediated resistance to lincomycin.
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The lmrB gene of Corynebacterium glutamicum, which confers specific resistance to lincosamides, such as lincomycin and clindamycin, was isolated. C. glutamicum cells, carrying the lmrB gene in a multicopy plasmid, showed increased resistance to lincomycin with a MIC of 230 microg/ml, which is a 9-fold increase compared to that of the wild type. The lmrB-disrupted mutant became sensitive to the compound. No difference in sensitivity to erythromycin, penicillin G, tetracycline, chloramphenicol, spectinomycin, nalidixic acid, gentamicin, streptomycin, ethidium bromide, and sodium dodecyl sulfate was observed. The protonophore carbonyl cyanide m-chlorophenylhydrazone abolished the lincomycin-resistance of lmrB-carrying cells. The putative protein product of the gene contained 14-transmembrane regions and showed high amino acid-sequence homology to the drug efflux pumps of other organisms. In addition, the putative protein contained a motif for major facilitators, suggesting a role in efflux-mediated resistance to lincomycin. (+info)
Enzymatic glycosylation of lincomycin.
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Lincomycin (1), a glycosidic antibiotic, active against Gram-positive bacteria, was modified enzymatically with the aim of improving its physico-chemical and biological properties. Compound 1 was glycosylated using jack bean alpha-mannosidase to produce 7-O-alpha-D-mannopyranosyl-lincomycin (2). (+info)
A critical role for the Var2 FtsH homologue of Arabidopsis thaliana in the photosystem II repair cycle in vivo.
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Using a var2-2 mutant of Arabidopsis thaliana, which lacks a homologue of the zinc-metalloprotease, FtsH, we demonstrate that this protease is required for the efficient turnover of the D1 polypeptide of photosystem II and protection against photoinhibition in vivo. We show that var2-2 leaves are much more susceptible to light-induced photosystem II photoinhibition than wild-type leaves. Furthermore, the rate of photosystem II photoinhibition in untreated var2-2 leaves is equivalent to that of var2-2 and wild-type leaves, which have been treated with lincomycin, an inhibitor of the photosystem II repair cycle at the level of D1 synthesis. This is in contrast to untreated wild-type leaves, which show a much slower rate of photosystem II photoinhibition due to an efficient photosystem II repair cycle. The recovery of var2-2 leaves from photosystem II photoinhibition is also impaired relative to wild-type. Using Western blot analysis in the presence of lincomycin we show that the D1 polypeptide remains stable in leaves of the var2-2 mutant under photoinhibitory conditions that lead to D1 degradation in wild-type leaves and that the abundance of DegP2 is not affected by the var2-2 mutation. We conclude, therefore, that the Var2 FtsH homologue is required for the cleavage of the D1 polypeptide in vivo. In addition, we identify a conserved lumenal domain in Var2 that is unique to FtsH homologues from oxygenic phototrophs. (+info)