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 small cysteine-rich 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). It is present but the disulfide bonds are reduced in the intracellular reticulate bodies (RBs). Was thought to be an outer membrane protein as it is part of a disulfide cross-linked complex that is insoluble in the detergent Sarkosyl. In PubMed:7532170 it was shown to likely be periplasmic.