Systematic analysis of an amidase domain CHAP in 12 Staphylococcus aureus genomes and 44 staphylococcal phage genomes

An alternative treatment for staphylococcal infections caused by antibiotic-resistance strains is to lyse staphylococci with peptidoglycan hydrolases, for example, a cysteine, histidine-dependent amidohydrolase/peptidase (CHAP). Here, CHAPs were analyzed in 12 Staphylococcus aureus genomes and 44 staphylococcal phage genomes. There are 234 putative CHAP-containing proteins and only 64 non-identical CHAP sequences. These CHAPs can be classified into phage CHAPs encoded in phages/prophages and bacterial CHAPs encoded on chromosomes and plasmids. The phage CHAPs contain a sequence signature 'F-[IV]-R', and the bacterial CHAPs mainly do not. The phage CHAPs are mostly positioned at the protein N-termini whereas the bacterial CHAPs are all positioned at the C-termini. The cell wall targeting domains LysM and SH3_5 are associated with the bacterial CHAPs and the phage CHAPs, respectively. The homology modeling reveals that five of six highly conserved residues are clustered at the putative active site and are exposed to the molecular surface.