The bacterial protein Mac 1 adopts an alpha/beta fold, with 14 beta strands and 9 alpha helices. The N-terminal domain is made up predominantly of alpha helices, whereas the C-terminal domain consists predominantly of beta sheets. Mac 1 blocks polymorphonuclear opsonophagocytosis, inhibits the production of reactive oxygen species and contains IgG endopeptidase activity [1].

1: Structure of the streptococcal endopeptidase IdeS, a cysteine proteinase with strict specificity for IgG. Wenig K, Chatwell L, von Pawel-Rammingen U, Bjorck L, Huber R, Sondermann P; Proc Natl Acad Sci U S A. 2004;101:17371-17376. PMID:15574492