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T.N. Patil J.N. Telford F.W. Plapp R.B. Koch 《Pesticide biochemistry and physiology》1979,12(1):95-104
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. 相似文献
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Chromatography, on methylated-albumin columns, of DNA from calf thymus, mouse testis, and Bacillus subtilis, yielded, on elution by a sodium chloride gradient, fractions differing in density. The fractions eluted by higher sodium chloride concentrations had lower densities in a CsCl density gradient. Since DNA with higher guaninecytosine content is eluted from the column with lower concentration of sodium chloride and has higher density, the density heterogeneity of DNA is best interpreted as a result of heterogeneity of base composition. An extra band observed in calf-thymus DNA had a higher density than that of the main DNA; it was eluted at a lower concentration of NaCl, indicating a higher content of guanine and cytosine. On the other hand, an additional DNA component in the mouse-testis DNA had a lower density and also it was eluted at a lower salt concentration, possibly an indication of an unusual base component in its structure. 相似文献
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