Mucopolysaccharide-polypeptide interactions: Effect of the position of the sulfate group

The differences in the interaction in solution of poly(l-lysine) with chondroitin 6-sulfate (chondroitin sulfate C) and with chondroitin 4-sulfate (chondroitin sulfate A) have been studied by circular dichroism spectroscopy. Both mucopolysaccharides force the poly(l-lysine) to adopt the α-helix in solution rather than the charged coil form expected at neutral pH. The observed spectra indicates that the polypeptide is at least 80% helical when the 6-sulfate form is present, but only about 20% α-helical in the presence of chondroitin 4-sulfate. Thus chondroitin66-sulfate has a stronger conformation directing effect on poly(l-lysine) than does the 4-sulfate, which is probably due to the different positions of the sulfate group on the polysaccharide c chain.