0STEOGENESIS-IMPERFE_37351

0STEOGENESIS-IMPERFE_37351 - OSTEOGENESIS IMPERFECTA...

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OSTEOGENESIS IMPERFECTA “Brittle Bone Disease” OI is an autosomal dominant genetic disease of poorly understood etiology. It manifests in several forms with varying degrees of severity ( types 1 - IV). Clinical features: -Extreme fragility of bone and proneness to fracture. -Pale blue sclera (white of the eye); deafness. -Abnormal shape of skull and laxity of ligaments. Biochemical abnormality : Defective synthesis of type 1 collagen. Collagen is a triple helix fibrous protein formed from two α 1(1)- and one α 2 (1) chains that provide the structural framework of bone matrix.
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Collagen ( Greek: glue producer) is the most abundant protein in mammals and accounts for 25-30% of protein content. Collagen is the main fibrous component of skin, bone, tendon, cartilage and teeth. There are ca. 20 different types of collagen molecules. It comprises about 90% of the organic matrix of the bone. Insoluble fibers of collagen have great tensile strength, which allows it to be the main stress-bearing component of connective tissues. It seems collagen appeared early in evolution and its composition and structure have changed relatively little, suggesting its design has reached optimum efficiency. COLLAGEN OVERVEW
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COLLAGEN STRUCTURE I All collagens are composed of 3 polypeptide alpha chains coiled around each other to form the tripe helix configuration. The individual polypeptide chains of collagen each contain approximately 1000 amino acid residues The collagen molecule is long (~3000 Ang.) and narrow (~1.4 Ang). Collagen has a distinctive amino acid composition:~one-third of its residues are Gly and 15-30% are Pro or 4-hydroxyprolyl (Hyl) residues. Small amounts of 3-hydroxyprolyl and 5-hydroxyprolyl residues, as well as hydroxylysine (OHLys) are also present. Some OHlys side chains are O- glycosylated by a disaccharide, galactosylglucose. The presence of Hyp confers stability on collagen through intramolecular hydrogen bonds that involve bridging water molecules. In the vitamin C (ascorbic acid) deficiency disease,
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0STEOGENESIS-IMPERFE_37351 - OSTEOGENESIS IMPERFECTA...

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