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Dev Growth Differ
1995 Oct 01;375:589-596. doi: 10.1046/j.1440-169X.1995.00014.x.
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Sea urchin fertilization stimulates CaM kinase-II (multifunctional [type II] Ca2+ /CaM kinase) activity and association with p34cdc2.
Tombes RM
,
Peppers LS
.
Abstract
Upon fertilization, the sea urchin egg synthesizes proteins which impart a Ca2+ dependence to M-phase onset. A potential target of this Ca2+ dependence may be CaM kinase-II (the multifunctional [type II] Ca2+ /calmodulin [CaM]-dependent protein kinase) which is necessary for nuclear envelope breakdown in fertilized sea urchin eggs. This study was intended to determine whether sea urchin CaMK-II is activated after fertilization and whether it interacts with other known M-phase regulators, such as p34cdc2 . We report that total CaMK-II activity, measured by solution assays, increases after fertilization, peaking just prior to cleavage. Interestingly, total CaMK-II activity continues to fluctuate, peaking again prior to second and third cleavage. Gel assays also reveal enhanced levels of the 56 and 62 kDa potential CaMK-II phosphoproteins after fertilization. Finally, CaMK-II activity and only the 62 kDa phosphoprotein physically associate with p34cdc2 , but again only after fertilization. These changes in CaMK-II activity and p34cdc2 -association after fertilization may ensure that Ca2+ signals are targeted to the M-phase machinery at the appropriate developmental times.