Sea urchin eggs possess a Ca+2-calmodulin dependent protein kinase which phosphorylates myosin of sea urchin or smooth muscle with light chains as the target. The enzyme is 400 KD in size with a single subunit of 56 KD. While detailed properties of the enzyme show that it is a myosin light chain kinase, it differs considerably from typical muscle (smooth or striated) kinases. It most resembles in properties the Ca+2-calmodulin kinases of brain in that it will phosphorylate casein, sea urchin tubulin and brain MAP-2, in addition to myosin light chains. We will investigate the egg for other calcium dependent kinases and will develop antibodies to the kinases we find. These will be used in a variety of studies. We will investigate the cell cycle dependence of kinase activity and enzyme quantity. We will seek antibodies which inhibit kinase activity and will utilize these in microinjection experiments into living eggs to see if we can inhibit specific stages such as chromosome separation or cleavage furrow formation. We will utilize the antibodies in localization studies in the egg at different stages in egg development and in early larval stages. Finally, we will compare the sea urchin egg kinases with those from clam eggs since these organisms are far apart in evolutionary origin and such studies will allow us to better understand how calcium and calmodulin participate in regulation of cellular processes.
