Alignment of bacterial pepsin homologues with human pepsin A and memapsins 1 and 2. Residues are numbered according to mature human pepsin A. Inserts relative to pepsin A are indicated by letters. Each active site residue (Asp32, Tyr75 and Asp215) is indicated by an asterisk. The hydrophobic-hydrophobic-Gly motifs in the psi-loops are indicated by ampersands. A disulphide bridge is indicated by a slash over one cysteine followed by a number and a backslash preceded by the same number over the second cysteine. The Chroma software  has been used to highlight residues according to amino acid properties and to generate the consensus line below each alignment block showing 80% conservation or more. Inserts found in only one sequence have been removed and are indicated by the number of amino acids excised in parentheses.