CONFORMATION, STABILITY AND INTERACTIONS OF CORNEAL KERATAN SULFATE PROTEOGLYCAN

We have monitored the molecular conformation, stability, interaction a nd dynamics of keratan sulfate proteoglycan, the major structural prot ein component of the cornea, in solution, by studying the fluorescence spectral features of its tryptophan residues as component-specific in trinsic spectral probes (collagen, the other structural component of t he cornea, has no tryptophans). Our study suggests that the Trp region of the molecule is in a motionally restricted environment as it exhib its a fluorescence red-edge effect and shows dipole relaxation. The ex trinsic spectral probe 8-anilinonaphthalene 1-sulfonate reveals kerata n sulfate proteoglycan to possess significant surface hydrophobicity. This dual character of keratan sulfate proteoglycan allows us to label it as an 'ambidextran' proteoglycan. The molecule is stable between p H 5-8 and has a T-m value of 72 degrees C. Disulfide bonds play a role in the stability of the molecule. KSPG is seen to interact with colla gen and the model compound, poly(L-proline), interaction of the proteo glycan with unilamellar vesicles appears to be more interfacial than p enetrative. This dual interaction displayed by KSPG with collagen and with lipid assemblages suggests that it plays the role of a 'filler' i n the extracellular matrix of the cornea.