A switch in disulfide linkage during minicollagen assembly in hydra nematocysts or how to assemble a 150-bar-resistant structure

Hydra minicollagen, the shortest collagen known, is an important component of the nematocyst wall, which has a very high tensile strength. It has an unusual structure, with small and closely related Cys-rich domains at both ends of its chains. Three chains are trimerized by a central collagenous domain. Polyhydroxyproline helices connect the Cys-rich domains with the collagenous domain. The minicollagen precursor contains three internal disulfide bridges in each Cys-rich domain and no disulfide bridges between chains of the same trimeric molecule or between different molecules. Biochemical and structural evidence as well as confocal immunofluorescence microscopy points to disulfide-mediated assembly during maturation of nematocysts. (C) 2002 Elsevier Science (USA).