Kihlberg B M, Cooney J, Caparon M G, Olsén A, Björck L
Department of Cell and Molecular Biology, Lund University, Sweden.
Microb Pathog. 1995 Nov;19(5):299-315. doi: 10.1016/s0882-4010(96)80003-9.
The mga regulon of Streptococcus pyogenes contains genes which contribute to the pathogenicity and virulence of this significant human pathogen. Transposon insertional inactivation of the regulatory mga gene in a S. pyogenes strain of the clinically important M1 serotype, blocked the expression of four genes located downstream of mga. These genes encode the M1 protein, the IgG-binding protein H, protein SIC which is an extracellular inhibitor of complement, and the C5a peptidase which interferes with granulocyte migration. The wild-type strain is resistant to phagocytosis and adheres to human skin tissue sections; properties that were lost in the transposon mutant. Moreover, the mutant was less virulent to mice but more cytolytic to human lymphocytes, the latter due to an increased activity of streptolysin S, whereas the production of streptolysin O, another toxin of S. pyogenes, was not affected. The mga mutation was complemented in trans with an intact mga gene which restored the phenotype of the wild-type strain.
化脓性链球菌的mga调控子包含有助于这种重要人类病原体致病性和毒力的基因。在具有临床重要性的M1血清型化脓性链球菌菌株中，调控性mga基因的转座子插入失活阻断了位于mga下游的四个基因的表达。这些基因编码M1蛋白、IgG结合蛋白H、作为补体细胞外抑制剂的SIC蛋白以及干扰粒细胞迁移的C5a肽酶。野生型菌株对吞噬作用具有抗性，并能黏附于人类皮肤组织切片；这些特性在转座子突变体中丧失。此外，该突变体对小鼠的毒力较低，但对人类淋巴细胞的细胞溶解作用更强，后者是由于链球菌溶血素S的活性增加，而化脓性链球菌的另一种毒素链球菌溶血素O的产生不受影响。用完整的mga基因对mga突变进行反式互补，恢复了野生型菌株的表型。
