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Category: Bacterial Pathogenesis
Ribosomes, Protein Synthesis Factors, and tRNA Synthetases, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817992/9781555812058_Chap22-1.gif /docserver/preview/fulltext/10.1128/9781555817992/9781555812058_Chap22-2.gifAbstract:
The biosynthesis and activity of the translational apparatus, encompassing rRNA, ribosomal proteins, tRNA, aminoacyl-tRNA synthetases, translation factors, and modifying enzymes, represent a major investment of cellular resources. This chapter summarizes available information about translational gene organization and expression in Bacillus subtilis and other gram-positive organisms, incorporating new information from the B. subtilis genome sequence, and provides comparisons to the extensive information available about these systems in Escherichia coli. Additional ribosomal protein genes are scattered around the genome, either alone or in small groups. All are transcribed in the same direction as DNA replication, with the exception of rpsD, rpsT, and rpmB. Translation elongation requires elongation factor (EF)-Tu to bring aminoacylated tRNA into the A site of the elongating ribosome, EF-Ts to recycle EF-Tu from its inactive GDP-bound state to the GTP-bound state required for tRNA binding, and EFG, which is required for translocation of the ribosome along the mRNA. There are 86 tRNA genes in the B. subtilis genome, most of which are organized in large rrn-associated clusters while others are scattered around the genome. The formylation of methionine on initiator tRNA-Met is carried out by the product of the fmt gene, which is located downstream of the def gene, the product of which removes the formyl group from the amino terminus of newly synthesized proteins.
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Gene organization in the major cluster of ribosomal protein genes. The major cluster in B. subtilis, located at around 12°, includes genes corresponding to the E. coli rif and str-spc clusters, which are located at 90 min and 74 min, respectively. Bent arrows indicate putative promoters, and stem loops indicate putative transcriptional terminators, identified by experimental analysis or inspection of the sequence (see text); in the E. coli str-spc cluster, // indicates a 17-kb region between tufA and rpsJ.
Gene organization in the major cluster of ribosomal protein genes. The major cluster in B. subtilis, located at around 12°, includes genes corresponding to the E. coli rif and str-spc clusters, which are located at 90 min and 74 min, respectively. Bent arrows indicate putative promoters, and stem loops indicate putative transcriptional terminators, identified by experimental analysis or inspection of the sequence (see text); in the E. coli str-spc cluster, // indicates a 17-kb region between tufA and rpsJ.
Ribosomal protein and rRNA genes in B. subtilis. Positions are based on a 360° map and are derived from the SubtiList database. The gene arrangement in the rif-stx-spc cluster is shown in Fig. 1 .
Ribosomal protein and rRNA genes in B. subtilis. Positions are based on a 360° map and are derived from the SubtiList database. The gene arrangement in the rif-stx-spc cluster is shown in Fig. 1 .
Ribosomal proteins
Ribosomal proteins
Translation factors
Translation factors
Ribosomal RNA operons
a tRNAs located between 16S and 23S regions.
b tRNAs located 3' of 5S region.
c tRNAA'e and tRNAoly located 5' of 16S region; tRNAMcl and tRNAAsp located 3' of 5S region.
Ribosomal RNA operons
a tRNAs located between 16S and 23S regions.
b tRNAs located 3' of 5S region.
c tRNAA'e and tRNAoly located 5' of 16S region; tRNAMcl and tRNAAsp located 3' of 5S region.
tRNA operons
a tmSL designation was used in SubtiList for new tRNA genes at multiple loci.
tRNA operons
a tmSL designation was used in SubtiList for new tRNA genes at multiple loci.
Processing and modification enzymes
Processing and modification enzymes
Aminoacyl-tRNA synthetases (AARS)
a T box genes in B. subtilis; all classes of AARS genes except LysRS and GltX can be found as T-box genes in various gram-positive species.
b GltX aminoacylates both tRNAGlu and tRNAGln with glutamate; Glu-tRNAGln is converted to Gln-tRNAGln by the Gat-CAB amidotransferase.
Aminoacyl-tRNA synthetases (AARS)
a T box genes in B. subtilis; all classes of AARS genes except LysRS and GltX can be found as T-box genes in various gram-positive species.
b GltX aminoacylates both tRNAGlu and tRNAGln with glutamate; Glu-tRNAGln is converted to Gln-tRNAGln by the Gat-CAB amidotransferase.