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.
Article| June 01 1983
A 72,000-mol-wt protein from tomato inhibits rabbit acto-S-1 ATPase activity.
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1983) 96 (6): 1761–1765.
M Vahey; A 72,000-mol-wt protein from tomato inhibits rabbit acto-S-1 ATPase activity.. J Cell Biol 1 June 1983; 96 (6): 1761–1765. doi: https://doi.org/10.1083/jcb.96.6.1761
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