title: Structural diversity in bacterial ribosomes: mycobacterial 70S ribosome structure reveals novel features.
abstract: Here we present analysis of a 3D cryo-EM map of the 70S ribosome from Mycobacterium smegmatis, a saprophytic cousin of the etiological agent of tuberculosis in humans, Mycobacterium tuberculosis. In comparison with the 3D structures of other prokaryotic ribosomes, the density map of the M. smegmatis 70S ribosome reveals unique structural features and their relative orientations in the ribosome. Dramatic changes in the periphery due to additional rRNA segments and extra domains of some of the peripheral ribosomal proteins like S3, S5, S16, L17, L25, are evident. One of the most notable features appears in the large subunit near L1 stalk as a long helical structure next to helix 54 of the 23S rRNA. The sharp upper end of this structure is located in the vicinity of the mRNA exit channel. Although the M. smegmatis 70S ribosome possesses conserved core structure of bacterial ribosome, the new structural features, unveiled in this study, demonstrates diversity in the 3D architecture of bacterial ribosomes. We postulate that the prominent helical structure related to the 23S rRNA actively participates in the mechanisms of translation in mycobacteria.
authors.affiliation: Structural Biology and Bio-Informatics Division, Indian Institute of Chemical Biology, Council of Scientific and Industrial Research, Jadavpur, Kolkata, West Bengal, India.
authors.forename: Manidip
authors.initials: M
authors.lastname: Shasmal
authors.forename: Jayati
authors.initials: J
authors.lastname: Sengupta
mesh_terms: D020285:Cryoelectron Microscopy / Q000379:methods; D008958:Models, Molecular; D008968:Molecular Conformation; D009161:Mycobacterium / Q000378:metabolism*; D020102:Mycobacterium smegmatis / Q000378:metabolism*; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012335:RNA, Ribosomal / Q000737:chemistry; D012269:Ribosomal Proteins / Q000737:chemistry; D054681:Ribosome Subunits, Large, Bacterial / Q000737:chemistry; D054680:Ribosome Subunits, Small, Bacterial / Q000737:chemistry; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D012335:RNA, Ribosomal; D012269:Ribosomal Proteins