Studies of Interaction between Chloroplast Coupling Factor 1 and Nucleotides by Circular Dichroism and Ultra-Violet Spectroscopies

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When ADP, CDP, GDP, IDP or UDP was mixed with chloroplast coupling factor 1 (CF_1) in the presence of MgCl_2, changes were induced in the ultraviolet absorption spectrum as well as the circular dichroism spectrum. These changes were about 70% complete in one minute. Also, these two changes were similar in the concentration curves of nucleotides, the competition between ADP with CDP, the inhibition by PP_i, and the requirement for divalent cations. A minor difference was also noted in the requirement for divalent cations by some of the nucleotides. The order of the affinities of these nucleotides for CF_1 was: ADP>CDP>UDP>IDP>GDP. The UV spectral changes induced by these nucleotides are interpreted as shifts of the absorption spectra of bound nucleotides by some 10 nm to longer wavelengths accompanied by decrease in absorbance. In difference CD spectra, negative peaks were found at about the same wavelengths of the absorption peaks of the respective nucleotides. Ca^<2+> was as effective as Mg^<2+> to these changes induced by ADP or GDP, but less effective than Mg^<2+> for those induced by CDP, UDP or IDP. In the presence of EDTA, the changes induced by ADP were somewhat lower and those induced by CDP. UDP or IDP became almost zero. However, the UV absorbance change induced by GDP was larger in the presence of EDTA than in the presence of Mg^<2+> or Ca^<2+>.
日本植物生理学会の論文