Non-collagenic structural glycoproteins.

Fibronectin is a dimer. Its subunits are joined anti-parallel by two disulfide bonds in the area of C-terminal ends. The peptide chain forms several globular domains. The molecules have an elongated shape and have binding sites with other molecules of fibronectin, with collagen, glycosaminoglycans, integrins.

Laminin is heterotrimer. Laminin molecule has a cruciform shape, with three short branches, each of which contains globular domains, and a long branch with a C-terminal globular domain. Laminin in basal membranes is in a complex with another protein – nidogene. Nidogen has binding sites of collagen. It provides the integration main components of the basement membrane. In the presence of Ca^{2 +} laminin by self-assembly forms tela due to the interaction of the globular domain of short branches.

4. Proteoglycans are high-molecular carbohydrate-protein compounds. They are up to 30% of the dry mass of connective tissue.

Polysaccharide group of proteoglycans called mucopolysaccharides(these substances are found mainly in the mucous substrates). Later they became known as glycosaminoglycans. These are linear unbranched polymers built of repeating disaccharide units. They are composed of glucosamine or galactosamine residues, as well as D-glucuronic or L-iduronic acid residues.

Firsthyaluronic acid was detected in the vitreous body.

It is built from the residues of glucuronic acid and N-acetylglucosamine. It is contained in the heart valves, cartilage. Its main function is the binding of water. It is involved in regulation of tissue permeability.

Chondroitin sulphates containe glucuronic acid and sulphuretted N-acetylgalactosamine. Chondroitin-6-sulphate is contained in the heart valves, and chondroitin-4-sulfate is contained in the cartilage.

Dermatan sulphate is found in the dermis (skin). L-iduronic acid is in the composition of dermatan sulphate. It is involved in the stabilization of collagen bundles.

Keratan sulphate was first isolated from bovine cornea. It does not contain D-glucuronic or L-iduronic acids. Keratan sulphates from different tissues have varying degrees of sulphonation and the type of connection to the protein.

Heparin is synthesized by mast cells. It exists in the form of single polysaccharide chains, or in the form of proteoglycans. Heparin is anticoagulant, it is involved in the regulation of blood clotting.

Date: 2016-04-22; view: 961