부산대학교 도서관

A protein fraction from the cellular slime mold Dictyostelium discoideum confers Ca 2+ -sensitivity on the activation of purified myosin adenosinetriphosphatase (ATP phosphohydrolase, EC 3.6.1.3) from Dictyostelium by purified Dictyostelium actin. That is, the fraction inhibits the actomyosin adenosine triphosphatase activity in the absence of Ca 2+ but not in the presence of Ca 2+ . This Ca 2+ -sensitizing factor affects only the actin-activated myosin adenosine triphosphatase and not the enzyme activity of myosin alone. The Ca 2+ -sensitivity is conserved when muscle actin replaces Dictyostelium actin, but is lost when muscle myosin replaces Dictyostelium myosin. The factor appears to be a protein since it is nondialyzable, is heat labile, and can be precipitated with ammonium sulfate. The factor can be purified 70-fold on an actin-affinity column.