The Structure and Function of Serum Opacity Factor: A Unique Streptococcal Virulence Determinant That Targets High-Density Lipoproteins

Figure 8

Variants of the Mga regulon and their relationship to preferential colonization of host sites. Mga (multigene activator) is a positive regulator of a number of streptococcal genes. The most prominent of these are the family of M proteins whose genes are tandemly linked. sof and sfbx are bicistronic and are also regulated by Mga, but are located some distance away. emm encodes for M protein, mrp encodes M-related proteins, enn encodes an M-like protein that binds IgA, and scpa encodes a C5a peptidase. Some serotypes contain only mga, emm, and scpa (pattern A). Other serotypes contain one or more of the remaining genes (patterns B–E). S. pyogenes with Mga patterns A, B, and C primarily infect oral tissues, whereas strains with pattern D are predominantly found in tissues of the skin. S. pyogenes with a pattern E Mga regulon are found at both oral and skin sites. Figure derived from data and classification scheme of Bessen and co-workers [47, 48].