RESUMO
Ribosomes from Mycobacterium tuberculosis (Mtb) possess species-specific ribosomal RNA (rRNA) expansion segments and ribosomal proteins (rProtein). Here, we present the near-atomic structures of the Mtb 50S ribosomal subunit and the complete Mtb 70S ribosome, solved by cryo-electron microscopy. Upon joining of the large and small ribosomal subunits, a 100-nt long expansion segment of the Mtb 23S rRNA, named H54a or the 'handle', switches interactions from with rRNA helix H68 and rProtein uL2 to with rProtein bS6, forming a new intersubunit bridge 'B9'. In Mtb 70S, bridge B9 is mostly maintained, leading to correlated motions among the handle, the L1 stalk and the small subunit in the rotated and non-rotated states. Two new protein densities were discovered near the decoding center and the peptidyl transferase center, respectively. These results provide a structural basis for studying translation in Mtb as well as developing new tuberculosis drugs.
Assuntos
Mycobacterium tuberculosis/química , Ribossomos/química , Microscopia Crioeletrônica , Modelos Moleculares , Movimento (Física) , Mycobacterium smegmatis/química , Inibidores da Síntese de Proteínas , Proteínas Ribossômicas/química , Subunidades Ribossômicas Maiores de Bactérias/química , Especificidade da EspécieRESUMO
Compound libraries have an important role in the drug discovery process. Various computational methods are available as decision support tools for medicinal chemists involved in compound library synthesis programs. These methods can be used to assemble a flexible library design scheme consisting of a structure-based library design followed by property-biased library refinement and final selection according to structure-activity-relationship considerations.