Burnens André P, Stanley John, Sack Ragna, Hunziker Peter, Brodard Isabelle, Nicolet Jacques
Institute for Veterinary Bacteriology, University of Berne, CH-3012 Berne, Switzerland.
Molecular Biology Unit, Virus Reference Division, Central Public Health Laboratory, London NW9 5HT, UK.
Microbiology (Reading). 1997 May;143 ( Pt 5):1539-1547. doi: 10.1099/00221287-143-5-1539.
The cloning and molecular genetic analysis of a locus mapping within the flagellar gene (fli) complex of Salmonella typhimurium is reported. A copy of the insertion element IS200 was located in a noncoding stretch of DNA upstream of the fliA gene. Comparative nucleotide sequence analysis showed that this copy of IS200 was 711 bp long and that its flanking regions contained no features common to other characterized insertion sites of this element. The element was located 37 bp downstream of an ORF whose product was shown by interspecific transfer and amino acid analysis to carry out N-methylation of selected lysine residues in Salmonella flagellin. The sequence and phenotype of this ORF identified it as fliB, encoding the only prokaryotic N-methylase acting on amino groups to have been characterized to date. It was found to be conserved among all clinically significant serovars of Salmonella. The IS200 insertion site is of particular interest since it was conserved in all but two rare evolutionary lines of S. typhimurium, and was absent from 85 Salmonella strains belonging to 37 other serovars. It is thus a phylogenetically significant marker at the serovar level.
本文报道了鼠伤寒沙门氏菌鞭毛基因（fli）复合体中一个位点的克隆及分子遗传学分析。插入元件IS200的一个拷贝位于fliA基因上游的一段非编码DNA区域。比较核苷酸序列分析表明，该IS200拷贝长711 bp，其侧翼区域没有该元件其他已鉴定插入位点共有的特征。该元件位于一个开放阅读框（ORF）下游37 bp处，通过种间转移和氨基酸分析表明，该ORF的产物可对沙门氏菌鞭毛蛋白中选定的赖氨酸残基进行N-甲基化。该ORF的序列和表型将其鉴定为fliB，它编码迄今为止已鉴定的唯一一种作用于氨基的原核N-甲基酶。研究发现它在所有具有临床意义的沙门氏菌血清型中都保守。IS200插入位点特别令人感兴趣，因为除了鼠伤寒沙门氏菌的两个罕见进化系外，它在所有菌株中都保守，并且在属于其他37个血清型的85株沙门氏菌中不存在。因此，它是血清型水平上具有系统发育意义的标记。
