| One feature common to all Cnidarians is the production of highly complex secretion products known as cnidae. It has been shown that all cnidae develop within a Golgi-derived vesicle of a cnidocyte. This vesicle, called the nematocyst primordium, at some time must contain all the molecules and ions that make up the structural material of the cnidae, the components of the venom, and other intracapsular components such as the cofactors or the enzymes that might be involved with vesicular biochemical modification relating to activity and assembly. Past studies have concentrated on ultrastructural changes during development, but little or no work has been done on the biochemical events underlying these processes. Only recently has work been done on the biochemistry of mature nematocyst capsules and threads.; This project addresses questions pertaining to the biochemistry of the nematocyst capsule wall and thread proteins. Early work on the chemistry of nematocyst capsules found the wall and tubule of the microbasic mastigophore nematocyst from Aiptasia pallida to be composed of a single collagen-like, 31.8 kd protein linked by disulfide bonds (Blanquet, 1966; Fishman and Levy, 1967; Phelan and Blanquet, 1985). Using Aiptasia, this thesis demonstrated, however, several disulfide bound, imino acid- and glycine-rich proteins, ranging in M{dollar}sb{lcub}rm r{rcub}{dollar} from 20 to 217 kd, with the major protein found at 40 kd. Similar analyses of structural proteins from the microbasic mastigophores of Metridium senile and the isorhizas of Physalia physalis reveal that the major protein obtained from each is also disulfide-linked, and has a similar molecular weight. Proteins obtained from the solubilization of microbasic mastigophores from Aiptasia pallida and Metridium senile appear more similar to each other than to those of Physalia physalis isorhizas, based on molecular weight, carbohydrate and sulfhydryl content. Analysis of nematocyst capsular and thread proteins, using monoclonal antibodies prepared for this purpose, confirmed suspected differences between nematocyst capsular and thread proteins, and also highlighted intraspecific differences among cnidae. Analyses of the reoxidation of reduced preparations of nematocyst structural proteins revealed an aggregation process that suggests possible mechanisms for nematocyst assembly in vivo. A model for wall development is proposed. |
