Caparon M G, Scott J R
Department of Microbiology and Immunology, Emory University Health Sciences Center, Atlanta, GA 30322.
Proc Natl Acad Sci U S A. 1987 Dec;84(23):8677-81. doi: 10.1073/pnas.84.23.8677.
By using Tn916 insertional mutagenesis, we have identified mry (M protein RNA yield), a gene required for high-level expression of the M protein, an essential virulence determinant of the group A streptococcus. The mry::Tn916 mutation causes a reduction by a factor of approximately equal to 50 in the amount of M protein produced, in the original strain and in a nonmutagenized host to which the mutation was transferred by transduction. The insertion is located approximately 1.8 kilobases upstream of the structural gene for M protein (emm) and its promoter. The genomic region including mry::Tn916 and emm was cloned on a cosmid vector and introduced into Escherichia coli. When the transposon excised precisely from the chimeric cosmid in E. coli, the resulting streptococcal DNA showed the same restriction pattern as the homologous chromosomal region in the parental nonmutagenized streptococcus. The sequence of the promoter for emm was not altered in the mry mutant. The reduction in protein correlates with a decrease in the amount of M protein-specific mRNA, indicating that mry regulates transcription of emm.
通过使用Tn916插入诱变技术，我们鉴定出了mry（M蛋白RNA产量）基因，它是A群链球菌重要毒力决定因子M蛋白高水平表达所必需的基因。mry::Tn916突变导致在原始菌株以及通过转导将该突变转移至的未诱变宿主中，M蛋白产生量减少约50倍。该插入位于M蛋白（emm）结构基因及其启动子上游约1.8千碱基处。包含mry::Tn916和emm的基因组区域被克隆到黏粒载体上，并导入大肠杆菌。当转座子在大肠杆菌中从嵌合黏粒上精确切除时，所得的链球菌DNA显示出与亲本未诱变链球菌中同源染色体区域相同的限制性图谱。在mry突变体中，emm启动子的序列未改变。蛋白质产量的降低与M蛋白特异性mRNA量的减少相关，表明mry调节emm的转录。
