The role of link-protein in the structure of cartilage proteoglycan aggregates

TLDR

Proteoglycan fractions from pig laryngeal cartilage were prepared and the influence of link‑protein on proteoglycan‑hyaluronate aggregate properties was assessed using viscometry and analytical ultracentrifugation. Link‑protein markedly stabilizes proteoglycan‑hyaluronate aggregates, rendering them resistant to neutral pH, temperatures up to 50 °C, and 4 M urea, and preventing displacement by hyaluronate oligosaccharides, thereby strengthening proteoglycan binding and effectively locking them onto the hyaluronate chain.

Abstract

Proteoglycan fractions were prepared from pig laryngeal cartilage. The effect of link-protein on the properties of proteoglycan-hyaluronate aggregates was examined by viscometry and analytical ultracentrifugation. Aggregates containing link-protein were more stable than link-free aggregates at neutral pH, at temperatures up to 50 degrees C and in urea (up to 4.0M). Oligosaccharides of hyaluronate were able to displace proteoglycans from link-free aggregates, but not from the link-stabilized aggregates. Both types of aggregate were observed in the ultracentrifuge, but at the concentration investigated (less than 2 mg/ml) the link-free form was partially dissociated and the proportion aggregated varied with the pH and temperature and required more hyaluronate for saturation than did link-stabilized aggregate. The results showed that link-protein greatly strengthened the binding of proteoglycans to hyaluronate and suggest that under physiological conditions it 'locks' proteoglycans on to the hyaluronate chain.