Collagen fibril aggregation-inhibitor from sea cucumber dermis

Collagen fibrils from the dermis of the sea cucumber Cucumaria frondosa are aggregated in vitro by the dermal glycoprotein stiparin (Trotter et al., 1 996). Under physiological ionic conditions stiparin appears to be both nece ssary and sufficient to cause fibrils to aggregate (Trotter et al., 1997). We report here the initial biochemical and biophysical characterization of a sulfated glycoprotein from C. frondosa dermis that binds stiparin and inh ibits its fibril-aggregating activity. This inhibitory glycoprotein, which has been named 'stiparin-inhibitor,' has the highest negative charge densit y of all the macromolecules extracted from the dermis. SDS-PAGE reveals thr ee similar to 31-kDa bands that stain with alcian blue but not with Coomass ie blue. Analytical ultracentrifugation indicates a native molecular weight of 62 kDa. Transmission electron microscopy of rotary-shadowed molecules s hows curved rods about 22 nm long. The glycoprotein does not bind collagen fibrils, but does bind stiparin with a 1:1 stoichiometry. The binding of st iparin-inhibitor to stiparin prevents the binding of stiparin to collagen f ibrils. The carbohydrate moiety produced by papain-digestion of the glycopr otein retains all of its inhibitory activity. The carbohydrate moiety of th e inhibitor is dominated by galactose and sulfate. (C) 1999 Published by El sevier Science B.V./International Society of Matrix Biology. All rights res erved.