Artificial phosphorylation removes Gelsolin's dependence on calcium.
Gelsolin is one of the best known actin-binding proteins with several distinct activities regulated by calcium. Using a kinase fraction isolated from mitotic HeLa cells, we found that the plasma form of gelsolin can be phosphorylated at a site located within the NH2-terminus region which does not exist in the cytoplasmic form. After this phosphorylation, gelsolin no longer requires Ca2+ for activity; it severs and subsequently caps actin filaments, and nucleates filament formation in Ca2+-free solution. These findings may clarify the mechanism of gelsolin regulation by Ca2+, and indicate that changes in electrical interactions between the NH2- and COOH-terminal ends are important for this regulation. Moreover, since only a single site is phosphorylated, and since the phosphorylated region does not contribute to this protein's own activity, the results suggest that a single chemical charge modification at a site away from the protein's core structure, such as this phosphorylation site, is sufficient to alter the protein's function.
Takiguchi
K
K
Department of Molecular Biology and Biochemistry, Rutgers University Piscataway, New Jersey, USA. j46037a@nucc.cc.nagoya-u.ac.jp
Yamashiro-Matsumura
S
S
Matsumura
F
F
D000199:Actins / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018260:Gelsolin / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D010766:Phosphorylation; D011817:Rabbits
D000199:Actins; D018260:Gelsolin; D002118:Calcium