FIGURE 8.

Schematic model of MUC2 polymer degradation by the protease RgpB. A, the MUC2 mucin forms a dense polymeric network upon secretion by the goblets cells in colon (1, 3). B, the MUC2 mucin polymer forms highly organized ring-like structures held together by disulfide linkage at the MUC2 N- and C-terminal regions. C, the central part of MUC2 consists of two mucin domains that are protected from proteolytic cleavage by its high glycosylation. Disruption of the mucus polymer at the termini is prevented by internal disulfide bonds. The position of the cleavage site Arg⁴³²⁰ identified in this study is found in between these two regions and would result in complete disruption of the mucus gel.