In elementary bodies (EBs, the infectious stage, which is able to survive outside the host cell) provides the structural integrity of the outer envelope through disulfide cross-links with the large cysteine-rich periplasmic protein and the major outer membrane porin. It has been described in publications as the Sarkosyl-insoluble COMC (Chlamydia outer membrane complex), and serves as the functional equivalent of peptidoglycan (By similarity). Part of a disulfide cross-linked outer membrane complex (COMC) composed of the major outer membrane porin (MOMP), the small cysteine-rich protein (omcA) and the large cysteine-rich periplasmic protein (omcB). The protein moiety probably penetrates into the periplasm. It is present but the disulfide bonds are reduced in the intracellular reticulate bodies (RBs). N-terminal amide-linked and S-diacylglycerol cysteine-linked to 16:0, 18:0, 15:0 branched, and 17:0 branched fatty acids (ratio 6:5:3:4) in the EB stage. The exact distribution of fatty acids has not been determined (By similarity). The N-terminus is blocked.