Identification of specific binding sites for keratan sulphate proteoglycans and chondroitin-dermatan sulphate proteoglycans on collagen fibrils in cornea by the use of cupromeronic blue in ‘critical-electrolyte-concentration’ techniques

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Abstract
Proteoglycans (PGs) in bovine corneal stroma were stained with Cupromeronic Blue in ''critical-electrolyte-concentration'' (CEC) methods for electron microscopy, and were located vis-a-vis collagen fibril a-e banding patterns. Keratanase and chondroitin ABC lyase digestion showed that a+c-band- and d+e-band-associated PGs were keratan sulphate-rich and chondroitin (dermatan) sulphate-rich respectively. The CEC pattern proved that the keratan sulphate PGs at the a and c bands differed. Comparison of their CECs with their behaviour or anion-exchange chromatography confirmed previous (indirect) attempts at identification [Scott and Haigh (1985) Biosci. Rep. 5, 765-774]. Similar arguments were applied to the dermatan sulphate PGs at the d and e bands. These results strongly support the one-PG-one-binding-site hypothesis [e.g. Scott (1988) Biochem. J. 252, 313-323]. Remarkable inter-species variations in the keratan sulphate PG patterns contrast with the relatively constant picture of dermatan sulphate PG-collagen fibril interactions.