The <i>mecA</i> regulatory locus is a three-component system.

<p>(A) Genetic organization of the <i>mecA</i> regulatory locus in major SCC<i>mec</i> types I–V and prototype MRSA strains used in this study. The magnified DNA sequence shows the two <i>mecR2</i> start codons in SCC<i>mec</i> type III and III (boxed), the stop codon (boxed), the four-thymine deletion in SCC<i>mec</i> type II (underlined), and the putative terminator (inverted arrows). (B) Multiple sequence alignment between the repressor of the xylose operon (XylR) and MecR2 from prototype SCC<i>mec</i> types II and III strains. Green – identical residues; red – similar residues; white – divergent residues. The figure was prepared using “The Sequence Manipulation Suite” freely available at <a href="http://www.bioinformatics.org" target="_blank">http://www.bioinformatics.org</a>.