Most M type 5 group A streptococcal strains were found to contain a single emm-like gene between virR and scpA (the Vir regulon), but two distinct emm-like genes were identified in the Vir regulon of the M5 strain NCTC8193. The complete sequences of both of these genes were determined. One, called emm5.8193, was shown to be a minor variant of the previously described emm5 gene from strain Manfredo. The second, designated enn5.8193, expresses an IgG-binding protein when cloned in Escherichia coli. A comparison of enn5.8193 with emm-like gene sequences from other strains indicated that it has a mosaic structure, consisting of distinct segments originating from emm-like genes in different OF+ and OF- strains. These data provide the first clear evidence that the horizontal transfer of emm-like sequences between distinct strains contributes to the evolution of group A streptococcal emm-like genes and Vir regulons.

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http://dx.doi.org/10.1111/j.1365-2958.1994.tb00316.xDOI Listing

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