Proposed resolution of the paradox of extensive crosslinking and low tensile strength of cuvierian tubule collagen from the sea cucumber Holothuria forskali

Abstract

The extruded tubules of the sea cucumber possess the amino acid composition, intermolecular crosslinking and fibre banding patterns typical of mammalian collagen fibres. Despite this resemblance, particularly the crosslinking normally associated with high tensile strength, the tubule fibres are extremely extensible. We suggest that the molecules are crosslinked through the normal head-to-tail mechanism but that further transverse crosslinking between the irregular fibrils is inhibited by the surrounding sheath of glycosaminoglycan, which also serves the purpose of a lubricant thus allowing slippage of adjacent fibrils under tension.