Fig. 10. Formation of the capsule wall formed from Nowa (green) and minicollagen (red). (A) Protein sorting and transport as detected by minicollagen antibody and mAb H22. Minicollagen and Nowa synthesized in the ER are transported in separate vesicles to the nematocyst vesicle. Nowa is detected by mAb H22 only modification by glycosylation in the Golgi apparatus and forms the outer wall. MTs (yellow) are organized in a scaffold around the growing part of the nematocyst, the MTOC is localized between the Golgi apparatus and the growing apex of the nematocyst. Minicollagen first accumulates in the capsule matrix and is then sorted to the wall to form the inner layer of the wall (3). By further transport of protein-filled vesicles, the outer tubule forms (4). It is subsequently invaginated into the cyst, and spines (s) are formed in the tubule lumen (5). Finally, minicollagen crosslinkage leads to a compaction of the wall structure (6). (B) Model of nematocyst patterning by the MT cytoskeleton. The growing part of the nematocyst vesicle is shown in a schematic cross-section. MTs form a cage around the vesicle and determine its shape (1). The outer wall formed by Nowa on the membrane (2) is used as template for minicollagen assembly. Soluble minicollagen trimers aggregate on the outer wall to form the inner wall (3-5). Finally, Nowa and minicollagen are crosslinked by disulfide bond isomerization to stabilize the structure (6).