Type X collagen, a product of hypertrophic chondrocytes.
The synthesis of collagen types IX and X by explants of chick-embryo cartilages was investigated. When sternal cartilage labelled for 24h with [3H]proline was extracted with 4M-guanidinium chloride, up to 20% of the 3H-labelled collagen laid down in the tissue could be accounted for by the low-Mr collagenous polypeptides (H and J chains) of type IX collagen; but no type X collagen could be detected. Explants of tibiotarsal and femoral cartilages were found to synthesize type IX collagen mainly in zones 1 and 2 of chondrocyte proliferation and elongation, whereas type X collagen was shown to be a product of the hypertrophic chondrocytes in zone 3. Pulse-chase experiments with tibiotarsal (zone-3) explants demonstrated a time-dependent conversion of type X procollagen into a smaller species whose polypeptides were of Mr 49 000. The processed chains [alpha 1(X) chains] were shown by peptide mapping techniques to share a common identity with the pro alpha 1(X) chains of Mr 59 000. No evidence for processing of type IX collagen was obtained in analogous pulse-chase experiments with sternal tissue. When chondrocytes from tibiotarsal cartilage (zone 3) were cultured on plastic under standard conditions for 4-10 weeks they released large amounts of type X procollagen into the medium. However, 2M-MgCl2 extracts of the cell layer were found to contain mainly the processed collagen comprising alpha 1(X) chains. The native type X procollagen purified from culture medium was shown by rotary shadowing to occur as a short rod-like molecule 148 nm in length with a terminal globular extension, whereas the processed species comprising alpha 1(X) chains of Mr 49 000 was detected by electron microscopy as the linear 148 nm segment.
D000818:Animals; D002356:Cartilage / Q000166:cytology / Q000378:metabolism*; D002642:Chick Embryo; D003094:Collagen / Q000096:biosynthesis*; D004591:Electrophoresis, Polyacrylamide Gel; D006984:Hypertrophy / Q000378:metabolism; D008854:Microscopy, Electron; D009924:Organ Culture Techniques; D010446:Peptide Fragments / Q000032:analysis; D011347:Procollagen / Q000096:biosynthesis; D011392:Proline / Q000378:metabolism
D010446:Peptide Fragments; D011347:Procollagen; D003094:Collagen; D011392:Proline