Isolation,characterization, and properties of factor F1 from mitochondrial preparations of housefly (Musca domestica L.) thorax |
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Authors: | T.N. Patil J.N. Telford F.W. Plapp R.B. Koch |
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Affiliation: | 1. Department of Biochemistry, Mississippi State University, Mississippi State, Mississippi 39762 USA;2. Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853 USA;3. Department of Entomology, Texas A&M University, College Station, Texas 77843 USA |
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Abstract: | A water-soluble Mg2+-dependent ATPase (coupling factor F1) was isolated from the mitochondria of housefly thorax. It comprised about 14% of the proteins from a crude preparation. The F1 preparation was nearly homogeneous as assessed by gel electrophoresis, isoelectric focusing, and electron microscopy. It was composed of five subunits with the following apparent molecular weights: α, 68,000; β, 61,000; γ, 38,000; δ, 27,000; and ?, 17,500. The isoelectric pH (pI) of this protein was 7.3. F1 had a pH optimum of 8.2 and a temperature optimum between 37 and 45°C. The enzyme was fairly stable at 25°C. Nearly complete loss of activity was noticed at 0°C, while at 0 or 25°C, glycerol (20%) partially stabilized the enzyme activity against such inactivation. The Km value of the enzyme with respect to ATP was 0.4 mM. The activity was stimulated by low concentrations of 2,4-dinitrophenol. The enzyme was inhibited by azide, p-hydroxymercuribenzoate, and guanidine hydrochloride. Oligomycin and the pesticides pyrethrin, cyhexatin, and DDT have no effect on the enzyme activity. However, all of these chemicals inhibited intact Mg2+- ATPase. The results are discussed in the light of differential responses of soluble and intact ATPase to these pesticides. |
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