Forum 01/15/2004

“Assembly of minicollagens in the Hydra Nematocyst”

Oliver Pertz, Research Associate – Department of Cell Biology, The Scripps Research Institute, La Jolla, CA

Nematocytes are jellyfishes and Hydra’s stinging cells. Nematocytes contain a complex organelle, the nematocyst, that consists of a capsule with a double-layered wall, an inverted tubule armed with spines and an operculum. Following appropriate stimulation, the capsule content is discharged leading to eversion of the tubule. This highly specialized form of exocytosis is one of the fastest event in nature, takes place in 10 us, generates an acceleration of 40000 g and is driven by a high internal pressure in the capsule (150 bar). The high internal pressure and extraordinary speed of tubule evagination suggests the need for high tensile strength in the capsule and tubule wall.

The major components of the capsule and tubule wall are small collagens molecules termed minicollagens. In this study, we recombinantly expressed a minicollagen, extensively characterized its biophysical properties and raised an antibody against it. This antibody enabled to immunolocalize this protein during the biogenesis of the nematocyst. This led to a model how this complex organelle is assembled under low pressure conditions, and then ultimately modified to resist the high internal pressure in the capsule.

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