Required for incorporation of cotE into the spore coat and for the formation of the outer layer. Has a cross-bridging function between cellulose and other coat proteins. Binds to cotE. Accumulates in prespore vesicles coordinately with other coat proteins. Expressed from 17.5 hours of development of the fruiting bodies. The N-terminal part (1-200) directs accumulation in prespore vesicles. The C-terminal part (333-532) binds cellulose and cotE simultaneously and specifies incorporation into the coat. O-glycosylated.