Sequence alignment of the amino-terminal domain of the proteins B. licheniformis 749/I BlaR1 (BlBlaR-NTD) and S. aureus RN4220 BlaR1 (SaBlaR-NTD) and S. aureus MRSA252 MecR (SaMecR-NTD).

The conserved residues are highlighted in red and the loop and transmembrane segments are marked: the transmembrane segments (TM1 to 4) in orange; the extracellular loops B1 (M¹-P⁸) and L2 (P⁵³-S¹¹⁵) in green and the cytoplasmic loops L1 (K²⁷-T³⁵) and L3 (Y¹³⁴-K³²²) in blue. The site of cleavage, situated between the R²⁹³ and R²⁹⁴ in S. aureus BlaR1, is indicated by an arrow.