Figure 2. Sequence alignment of Spy0129 with other class B sortases.

Invariant residues are highlighted in dark blue and conserved residues in lighter blue colours. Putative catalytic residues are coloured in purple. The secondary structure elements from Spy0129 are shown above the sequence. Residues corresponding to the sortase signature motif are boxed with a black outline. The β6/β7 loop region of S. aureus SrtB which was shown to confer substrate specificity is outlined with a dotted red box.