Malate regulation of Mg2+-ATPase of chloroplast coupling factor 1 |
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Authors: | Hui-Miao Ren Jia-Mian Wei Yun-Kang Shen |
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Affiliation: | (1) Shanghai Institute of Plant Physiology, Chinese Academy of Sciences, 300 Fenglin Road, 200032 Shanghai, China |
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Abstract: | The regulatory effects of malate on chloroplast Mg2+-ATPase were investigated and the mechanism was discussed. Malate stimulated methanol-activated membrane-bound and isolated CF1 Mg2+-ATPase activity. The subunit of CF1 may be involved in malate regulation of the enzyme function. Modification of subunit at one site of the peptide by NEM may affect malate stimulation of ATPase while at another site may have no effect. The effect of malate on the Mg2+-ATPase was also controlled by the Mg2+/ATP ratio in the reaction medium. The enhancing effect of malate on Mg2+-ATPase activity depended on the presence of high concentrations of Mg2+ in the reaction mixture. Kinetic study showed that malate raised the Vmax of catalysis without affecting the Km for Mg2+ ATP. The experiments imply that the stimulation of Mg2+-ATPase by malate is probably correlated with the Pi binding site on the enzyme. The regulation of ATPase activity by malate in chloroplasts may be relevant to its function in vivo.Abbreviations CF1 chloroplast coupling factor 1 - CF1 (-) and CF1 (-) CF1 deficient in the and subunit - MF1 mitochondria coupling factor 1 - NEM N-ethylmaleimide - PMS phenazine methosulfate - OG n-octyl--d-glucopyranoside |
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Keywords: | CF1 chloroplast malate Mg2+-ATPase Mg2+/ATP ratio spinach |
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