[The byssus of Mytilus: electrophoresis of hydroxyproline-rich proteins from the "collagen gland"].

An hydroxyproline rich fraction has been extracted from the byssus gland of Mytilus. This fraction could be the intracellular precursor of the "secreted collagen" found in the byssus threads. Its molecular weight, estimated through SDS gel electrophoresis, appears lower than that of a chains of mesenchymal collagen.