Spanier J G, Jones S J, Cleary P
Science. 1984 Aug 31;225(4665):935-8. doi: 10.1126/science.6089334.
The M protein is the antigen on the surface of group A streptococci that allows these bacteria to resist phagocytosis. DNA encoding the M12 protein was cloned into Escherichia coli and used as an isotopically labeled hybridization probe to compare genomic DNA's isolated from M+ and M- isogenic cultures in an effort to elucidate the genetic basis of this variation. DNA's from two spontaneous, independent M- variants contained small (approximately 50 base pairs) deletions which were mapped to identical restriction fragments within or adjacent to the M protein coding sequence. Taken together with the pleiotropic nature of these deletions, this suggests that they define a regulatory switch.
M蛋白是A组链球菌表面的抗原，它使这些细菌能够抵抗吞噬作用。编码M12蛋白的DNA被克隆到大肠杆菌中，并用作同位素标记的杂交探针，以比较从M +和M-同基因培养物中分离出的基因组DNA，从而阐明这种变异的遗传基础。来自两个自发、独立的M-变体的DNA含有小的（约50个碱基对）缺失，这些缺失被定位到M蛋白编码序列内或相邻的相同限制性片段上。结合这些缺失的多效性，这表明它们定义了一个调节开关。
