Vahey M
J Cell Biol. 1983 Jun;96(6):1761-5. doi: 10.1083/jcb.96.6.1761.
Tomato activation inhibiting protein (AIP) is a molecule of an apparent molecular weight of 72,000 that co-purifies with tomato actin. In an assay system containing rabbit skeletal muscle F-actin and rabbit skeletal muscle myosin subfragment-1 (myosin S-1), tomato AIP dissociated the acto-S-1 complex in the absence of Mg+2ATP and inhibited the ability of F-actin to activate the low ionic strength Mg+2ATPase activity of myosin S-1. At a molar ratio of 5 actin to 1 AIP, a 50% inhibition of the actin-activated Mg+2ATPase activity of myosin S-1 was observed. The inhibition can be reversed by raising the calcium ion concentration to 1 X 10(-5) M. The AIP had no effect on the basal low ionic strength Mg+2ATPase activity of myosin S-1 in the absence of actin. The protein did not bind directly to actin nor did it cause depolymerization or aggregation of F-actin but appeared, instead, to interact with the actin binding site on myosin S-1. Since AIP is a potent, reversible inhibitor of the rabbit acto-S-1 ATPase activity, it is postulated that it may be responsible for the low levels of actin activation exhibited by tomato F-actin fractions containing the AIP.
番茄激活抑制蛋白（AIP）是一种表观分子量为72,000的分子，它与番茄肌动蛋白共同纯化。在含有兔骨骼肌F-肌动蛋白和兔骨骼肌肌球蛋白亚片段-1（肌球蛋白S-1）的测定系统中，番茄AIP在没有Mg+2ATP的情况下使肌动蛋白-S-1复合物解离，并抑制F-肌动蛋白激活肌球蛋白S-1的低离子强度Mg+2ATP酶活性的能力。在肌动蛋白与AIP的摩尔比为5:1时，观察到肌球蛋白S-1的肌动蛋白激活的Mg+2ATP酶活性受到50%的抑制。通过将钙离子浓度提高到1×10(-5)M可以逆转这种抑制作用。在没有肌动蛋白的情况下，AIP对肌球蛋白S-1的基础低离子强度Mg+2ATP酶活性没有影响。该蛋白不直接与肌动蛋白结合，也不会导致F-肌动蛋白的解聚或聚集，而是似乎与肌球蛋白S-1上的肌动蛋白结合位点相互作用。由于AIP是兔肌动蛋白-S-1 ATP酶活性的一种有效、可逆的抑制剂，因此推测它可能是含有AIP的番茄F-肌动蛋白组分中肌动蛋白激活水平较低的原因。
