Cytoskeletal proteins working in the process of secretion

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1. Characterization of the cytoskeletal proteins of adrenal medulla. A new actin binding protein was found and purified from the membrane fraction of adrenal medulla. This protein was assumed to be a G-protein, for this protein was solubilized from the membrane fraction using GTP S, a nonhydrolyzable GTP analogue. Immunoblotting experiments using antibodies against known G proteins, such as Gi, Go, and Gs, however, showed no reactivity with this protein and antibody prepared against this protein showed also no reactivity with these G-proteins. A structural analysis of this protein is now under progress.2. Analysis of membrane proteins of the central nervous system. A new protein, rich in the membrane fraction of brain tissue and having a calmodulin binding activity, was purified and its molecular structure was clarified by cDNA cloning. This protein was an acidic protein having a unique amino acids composition containing few hydrophobic residues and showed resistance to heat and acid treatments. These characters resemble to these of MARCKS and GAP-43. In its N-terminal end, this protein has a myrystoylation site and the addition of this lipid is thought to be responsible to its translocation to the cell membrane. Studies using specific antibody showed its specific expression in the nervous tissue, its developmentally changed expression and its localization in the membrane of the neuron.