RESUMO
We demonstrate that the antibiotic amicoumacin A (AMI) is a potent inhibitor of protein synthesis. Resistance mutations in helix 24 of the 16S rRNA mapped the AMI binding site to the small ribosomal subunit. The crystal structure of bacterial ribosome in complex with AMI solved at 2.4 Å resolution revealed that the antibiotic makes contacts with universally conserved nucleotides of 16S rRNA in the E site and the mRNA backbone. Simultaneous interactions of AMI with 16S rRNA and mRNA and the in vivo experimental evidence suggest that it may inhibit the progression of the ribosome along mRNA. Consistent with this proposal, binding of AMI interferes with translocation in vitro. The inhibitory action of AMI can be partly compensated by mutations in the translation elongation factor G.
Assuntos
Antibacterianos/química , Cumarínicos/química , Biossíntese de Proteínas/efeitos dos fármacos , Inibidores da Síntese de Proteínas/química , Estabilidade de RNA , Antibacterianos/farmacologia , Proteínas de Bactérias/genética , Sequência de Bases , Sítios de Ligação , Cumarínicos/farmacologia , Cristalografia por Raios X , Farmacorresistência Bacteriana , Escherichia coli , Testes de Sensibilidade Microbiana , Modelos Moleculares , Fator G para Elongação de Peptídeos/genética , Inibidores da Síntese de Proteínas/farmacologia , RNA Mensageiro/metabolismo , Subunidades Ribossômicas Maiores de Bactérias/química , Subunidades Ribossômicas Menores de Bactérias/química , Staphylococcus aureus/genética , Thermus thermophilusRESUMO
The study of an archived sample of crystallomycin complex using HPLC, ESI HRMS, and 2D NMR showed that two major components of the antibiotic, compounds 1 and 2, are lipopeptides having the same peptide core, Asp1-cyclo(Dab2-Pip3-MeAsp4-Asp5-Gly6-Asp7-Gly8-Dab9-Val10-Pro11-), N-acylated either with Δ3-iso-tetradecenoyl or Δ3-anteiso-pentadecenoyl that are identical to aspartocins C and B, respectively. According to the 2D NMR study, compound 2 in DMSO solution exists as a mixture of four conformers. The producing strain was identified as Streptomyces griseorubens. Compounds 1 and 2 have considerable Ca2+-dependent activity against Gram-positive bacteria including five MRSA strains.