Ji Y E, Colston M J, Cox R A
Laboratory of Developmental Biochemistry, National Institute for Medical Research, Mill Hill, London, UK.
Microbiology (Reading). 1994 Jan;140 ( Pt 1):123-32. doi: 10.1099/13500872-140-1-123.
Slow-growing mycobacteria have a single ribosomal RNA (rrn) operon, with the genes for 16S, 23S and 5s rRNA being present in that order. The transcription start site of the rrn operon of Mycobacterium tuberculosis was identified in Escherichia coli. PCR methodology was used to amplify parts of the rrn operon, namely the leader region and the spacer-1 region separating the 16S rRNA and 23S rRNA genes of Mycobacterium avium, Mycobacterium paratuberculosis, Mycobacterium intracellulare, 'Mycobacterium lufu', Mycobacterium simiae and Mycobacterium marinum. The amplified DNA was sequenced. The sequence data, together with those obtained previously for Mycobacterium leprae and M. tuberculosis, were used to identify putative antitermination signals and RNase III processing sites within the leader region. Notable features include a highly conserved Box B element and a sequence of 31 nucleotides which is common to all eight slow-growers which were scrutinized. A secondary structure for mycobacterial precursor-16S rRNA was devised, based on sequence homologies and homologous nucleotide substitutions. The 18 nucleotides at the 5'-end of spacer-1 have the capacity of binding sequences close to the 5'- and 3'-ends of mature 16S rRNA, suggesting that secondary structure is important to the maturation process. All the slow-growers, including M. leprae, conform to the same scheme of secondary structure. The scheme proposed for M. tuberculosis is a variant of the main theme. The leader and spacer sequences may prove a useful supplement to 16S rRNA sequences in establishing phylogenetic relationships between very closely related species. 'M. lufu' appears to be a close relative of M. intracellulare.
生长缓慢的分枝杆菌有一个单一的核糖体RNA（rrn）操纵子，其中16S、23S和5S rRNA的基因按此顺序排列。结核分枝杆菌rrn操纵子的转录起始位点在大肠杆菌中被鉴定出来。采用聚合酶链反应（PCR）方法扩增了rrn操纵子的部分区域，即鸟分枝杆菌、副结核分枝杆菌、胞内分枝杆菌、“鲁夫分枝杆菌”、猿分枝杆菌和海分枝杆菌中分隔16S rRNA和23S rRNA基因的前导区和间隔区-1。对扩增的DNA进行了测序。序列数据与先前获得的麻风分枝杆菌和结核分枝杆菌的数据一起，用于鉴定前导区内假定的抗终止信号和核糖核酸酶III加工位点。显著特征包括一个高度保守的Box B元件和一个在所有被研究的8种生长缓慢的分枝杆菌中都共有的31个核苷酸序列。基于序列同源性和同源核苷酸取代，设计了分枝杆菌前体-16S rRNA的二级结构。间隔区-1 5'端的18个核苷酸能够与成熟16S rRNA 5'端和3'端附近的序列结合，这表明二级结构对成熟过程很重要。所有生长缓慢的分枝杆菌，包括麻风分枝杆菌，都符合相同的二级结构模式。为结核分枝杆菌提出的模式是主要模式的一个变体。在前导区和间隔区序列在建立亲缘关系非常密切的物种之间的系统发育关系时，可能是对16S rRNA序列的一个有用补充。“鲁夫分枝杆菌”似乎是胞内分枝杆菌的近亲。
