Effect of calyculin A on the surface structure of unfertilized sea urchin eggs |
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Authors: | Tosuji H Miyaji K Fusetani N Nakazawa T |
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Affiliation: | Department of Chemistry and BioScience, Faculty of Science, Kagoshima University, Kagoshima, Japan. tosuji@sci.kagoshima-u.ac.jp |
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Abstract: | Calyculin A, a potent inhibitor of type 1 and type 2A protein phosphatases, induces contractile ring formation when applied to unfertilized sea urchin eggs [Tosuji et al., 1992: Proc. Natl. Acad. Sci. USA 89:10613-10617]. We report here the elongation of microvilli in the unfertilized eggs exposed to calyculin A. The elongated microvilli and associated sperm-egg binding sites (egg receptor for sperm) then became concentrated into a constriction site corresponding to the cleavage furrow. The egg receptor for sperm was also in close connection to the microfilaments. Okadaic acid is another known inhibitor of protein phosphatase type-1 and type-2A. Its effect, however, is about a hundredfold feebler for type-1 phosphatase than type-2A. Even after treatment with okadaic acid, no change was observed, suggesting that these morphological changes were induced by calyculin A solely though its inhibitory effect on the type-1 protein phosphatase. |
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