Analysis of Membrane-Associated Proteoglycans

Proteoglycans solubilized by protease digestion are often degraded making it difficult to extrapolate structural data obtained on analysis of the digested proteoglycan to the native molecule. For these reasons, alternative methods have been adopted for the solubilization and characterization of cell membrane-associated proteoglycans. Some of these methods will be described in this chapter. Cell surface proteoglycans may occur either as intercalated molecules where the core protein is anchored in the plasma membrane or as peripheral proteoglycans associated with the membrane either via the polysaccharide chains or the core protein. Membrane-intercalated proteoglycans solubilized in the presence of detergents will have the hydrophobic part of the core protein associated with a detergent micelle. Because most peripheral membrane proteins will not associate with detergent micelles, this property is a useful indication of a hydrophobic membrane anchor. To demonstrate association of a particular proteoglycan with a detergent micelle, one may use the fact that detergents form micelles of different sizes.