Immune inhibitor A (InhA)-type metallopeptidases are potential virulence factors secreted by members of the Bacillus cereus group (BGC) and belong to the thuringilysin family within the metzincin clan of metallopeptidases, M6 in the MEROPS database. The structure revealed four domains: a pro-peptide, a catalytic domain, a domain reminiscent of viral envelope glycoproteins (VEG) and a MAM domain grafted into the latter [1]. This entry represents the MAM domain found in InhA and PrtV peptidases from Vibrio (a slightly more distant thuringilysin family members), which is required for proper protein expression and has certain flexibility. It is a beta-sandwich consisting of two five-stranded antiparallel beta-sheets, grafted between the second and third strands of the upper sheet of VEG [1]. This domain displays closest structural similarity with MAM domains such as the one from the human MP, meprin beta.

1: Structural Basis for Latency and Function of Immune Inhibitor A Metallopeptidase, a Modulator of the Bacillus anthracis Secretome. Arolas JL, Goulas T, Pomerantsev AP, Leppla SH, Gomis-Ruth FX; Structure. 2016;24:25-36. PMID:26745529