sulfaatproteoglycan

Sulfate proteoglycans are a class of complex macromolecules found in the extracellular matrix of animals and in the cell walls of some bacteria. They are characterized by a core protein to which glycosaminoglycan (GAG) chains are covalently attached. These GAG chains are long, unbranched polysaccharides composed of repeating disaccharide units, one of which is always a hexosamine. The defining feature of sulfate proteoglycans is the presence of sulfate groups esterified to hydroxyl groups on the sugar residues of the GAG chains. These sulfate groups are typically negatively charged at physiological pH, contributing significantly to the overall charge density of the molecule.

The structure of sulfate proteoglycans varies widely depending on the specific core protein and GAG chains involved. Common GAGs found in sulfate proteoglycans include chondroitin sulfate, keratan sulfate, dermatan sulfate, and heparan sulfate. The attachment of GAGs to the core protein occurs through a specific linker region, often initiated by a trisaccharide. The core protein itself can be quite large and possesses domains that mediate interactions with other extracellular matrix components, cell surface receptors, and growth factors.

Sulfate proteoglycans play crucial roles in a variety of biological processes. Their highly hydrated nature, due to the negatively charged sulfate groups, allows them to form a gel-like matrix that provides structural support and resists compression, particularly important in connective tissues like cartilage and bone. They are also involved in cell adhesion, cell signaling, and the regulation of growth factor activity. Furthermore, certain sulfate proteoglycans, like heparan sulfate, are found on cell surfaces and can interact with a wide range of signaling molecules, influencing cellular behavior and development.