Abstract
Thrombospondin-5 (TSP5) is found in cartilage and appears at specific times, distinct from type II collagen, during chondrogenesis. Anchorage in the cartilage matrix appears to be dependent on divalent cations and it is preferentially localized in the territorial matrix surrounding chondrocytes. TSP5 is found in all cartilages and in the vitreous of the eye, and mutations in the gene cause pseudochondroplasia and multiple epiphyseal dysplasia. TSP5 consists of five disulphide-bonded subunits (each of approximate molecular weight 100,000), which give a molecular mass of 524kDa by sedimentation equilibrium centrifugation. Each subunit contains a peripheral globular domain, a flexible strand of epidermal growth factor (EGF) and type III repeats, and an assembly domain where the five arms meet. There are four six-cysteine EGF repeats and seven type 3 repeats. TSP5 can be isolated from 4мguanidine-HCl extracts of cartilage by CsCl-density gradient centrifugation, Sephadex G-200 chromatography, DEAE-cellulose chromatography, and can be purified by passing through gelatin-Sepharose and heparin-Sepharose columns. It has also been extracted from adult human cartilage in EDTA-containing buffers; DEAE-Sepharose and Sepharose CL 4-B chromatography; and heparin affinity chromatography.
Published Version
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