Ribosomal protein genes of Micrococcus luteus : organization and novel codon usage 単球菌のリボソーム蛋白遺伝子に関する研究 : 遺伝子構造と新しい遺伝暗号選択型について

博士論文

The DNA sequence of the Micrococcus luteus str-operon, that includes genes for ribosomal proteins S12 (str or rpsL) and S7 (rpsG)and elongation factors G (fus) and Tu (tuf), has been determined and compared with the corresponding sequence of E. coli to see the effect of high genomic GC-content(74%) of M. luteus on the codon usage pattern. The gene organization in this operon and the deduced amino acid sequence of the corresponding proteins are well conserved between the two species. Codon GUG is used for initiation for S12, EF-G and EF-Tu, and AUG is used only for S7, whereas GUG is present only for one of the EF-Tu's in E. coli. The complete DNA sequences of the Micrococcus luteus spc-operon and its adjacent regions has also been determined. The sequence has revealed the presence of genes that are homologous to those of the E. coli ribosomal and related proteins, L14, L24, L5, S8, L6, L18, S5, L30, L15 and secretion protein Y (secY), and the gene for adenylate kinase (adk). The gene arrangement in the spc-operon is essentially the same as that of E. coli except for the absence in the M. 1uteus spc-operon of the genes for S14 and X protein that exist in the E.coli spc-operon. SecY and adk seem to be composed of another operon(adk-operon) with at least an open reading frame. The deduced amino acid sequences for these ribosomal proteins are well conserved among the two specie (40 – 65% identity). Reflecting a high genomic guanine and cytosine (GC)-content of M. luteus (74%), the codon usage of the genes is extremely biased to use G and C, about 94% of the codon third positions being G or C. Seven codons, AUA, AAA, AGA,UUA, GUA, CUA and,CAA, all of which have A at the codon third positions, are completely absent in the M. luteus genes examined. Out of 15 genes in the M. 1uteus str-, spc- and adk-operons, eight (thirteen) use GUG (UGA) and seven (two) use AUG (UAA) as initiation (termination) codon.

名古屋大学博士学位論文 学位の種類:理学博士(課程) 学位授与年月日:平成1年2月25日