| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1987: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1986: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
A cell-aggregating activity was extracted as a gigantic sugarprotein complex from the supernatant of cell dissociation of a sea urchin embryo, Hemicentrotus pulcherrimus. A Ca-binding protrein was isolated from the complex by DEAE-cellulose and purified. It was an acidic glycoprotein(pI 3) around 1,000K. It bound ^<45>Ca pH dependently, maximal at the pH of sea water(pH 8) and the dissociation constant was 4x10^<-4> M. From amino acid analysis, it was shown to be a gla-protein containing 0.5% of -carboxyglutamic acid. Inhibitors of gla-protein were shown to disturb cell adhesion in vitro and in situ.
On the other hand, the binding of this Ca-binding protein to the cell surface was shown to be mediated by another mechanism. The embryos of H. pulcherrimus was shown to be dissociated species-specifically by the wheat germ agglutinin(WGA). And the cell reaggregation by this protein was inhibited by GlcNAc. Also, the Ca-binding protein competed with WGA in hemagglutination.
WGA receptor was extracted by the aid of detergent from dissociated cells and purified. It reacted with the Ca-binding protein and disturbed cell adhesion in situ. Accordingly, it is assumed to be the cell surface receptor for the Ca-binding protein.
In conclusion, the cell adhesion molecule of sea urchin embryo was shown to be a bifunctional glycoprotein containing Ca-binding and sugarbinding domains.
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