Mga is an urban locality (an urban-type settlement) in Kirovsky District of Leningrad Oblast, Russia. Population:
The name is almost certainly derived from the identically named Mga River on which it lies (which in turn is probably of Finno-Ugric origin); the suggestion that it comes from the initials of the owner of the land in the 19th century, Maria Grigorievna Apraksin (a member of the same family for which the Apraksin Dvor in St. Petersburg is named), is extremely unlikely.
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.