RESUMEN
A novel series of 10-hydroxyl ketolide derivatives were synthesized, during which a distinctive intermediate, 3-O-descladinosyl-3-oxo-11-deoxy-10,11-epoxy-6-O-methylerythromycin A, was obtained from 6-O-methylerythromycin A. The structure and stereochemistry of this novel structure were confirmed via NMR and X-ray crystallography. Moreover, antibacterial evaluations were established in order to assess our modifications and acquire a deep understanding of the ketolides' structure-activity relationship (SAR).
Asunto(s)
Antibacterianos/síntesis química , Cetólidos/química , Antibacterianos/química , Antibacterianos/farmacología , Bacterias/efectos de los fármacos , Sitios de Unión , Claritromicina/química , Cristalografía por Rayos X , Evaluación Preclínica de Medicamentos , Cetólidos/síntesis química , Cetólidos/farmacología , Espectroscopía de Resonancia Magnética , Pruebas de Sensibilidad Microbiana , Conformación Molecular , Simulación del Acoplamiento Molecular , Peptidil Transferasas/química , Peptidil Transferasas/metabolismo , Estructura Terciaria de Proteína , Relación Estructura-ActividadRESUMEN
A DNA fragment containing the Escherichia coli 5S rDNA sequence linked to a T7 promoter was prepared by PCR from an M13 clone carrying the 5S-complementary sequence. The DNA was transcribed with T7 polymerase using a mixture of [alpha-32P]UTP and 4-thio-UTP, yielding a transcript in which approximately 18% of the uridine residues were randomly replaced by thiouridine. This modified 5S RNA could be reconstituted efficiently into 50S ribosomal subunits or 70S functional complexes. The reconstituted particles were irradiated at wavelengths above 300 nm, and the crosslinked ribosomal components were identified. A crosslink in high yield was reproducibly observed between the modified 5S RNA and 23S RNA, involving residue U-89 of the 5S RNA (at the loop end of helix IV) linked to nucleotide 2477 of the 23S RNA in the loop end of helix 89, immediately adjacent to the peptidyltransferase "ring." On the basis of this result, and in combination with earlier immunoelectron microscopic data, we propose a model for the orientation of the 5S RNA in the 50S subunit.