OCCURRENCE OF FIBRILLAR COLLAGEN WITH STRUCTURE OF (ALPHA(1))(2) ALPHA(2) IN THE TEST OF SEA-URCHIN ASTHENOSOMA-IJIMAI

Test collagen from the sea urchin Asthenosoma ijimai was disaggregated into collagen fibrils in a neutral salt solution containing beta-merc aptoethanol, solubilized by limited pepsin digestion and isolated by s elective precipitation with NaCl. The test collagen was mostly rendere d soluble and found to consist of two distinct alpha-chains, alpha(1) and alpha(2), which could be isolated by CM-cellulose chromatography f ollowed by Sepharose CL-4B gel filtration. Each of the alpha-chains ha d a molecular mass of about 100 kDa and the alpha(1)- and alpha(2)-cha ins existed in a molar ratio of about 2:1, indicating the occurrence o f(alpha(1))(2) alpha(2) heterotrimers. This was confirmed by amino aci d analyses of the isolated alpha-chains. From these results, the fibri llar collagen of sea urchin test appears to share common characteristi cs, such as precipitation properties with NaCl, chromatographic and el ectrophoretic behaviours and subunit composition with vertebrate type- I collagen. This type of fibrillar collagen was also found in other sp ecies of sea urchins.