Mga is a DNA-binding protein that activates the expression of several important virulence genes in Streptococcus pyogenes (group A Streptococcus, GAS) in response to changing environmental conditions. The family also contains VirR like proteins which match only at the C-terminus.
Mga is a wide-reaching regulator, affecting gene expression in over 10% of the S. pyrogenes genome. The other large regulator of virulence in GAS is the CovR/S two-component system, which affects the expression of approximately 15% of the genome. The two systems are linked through another protein, RivR, and a small non-coding RNA RivX.
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