Ultraviolet absorption spectrum change induced by the interaction between chloroplast coupling factor 1 and ADP or ATP
1980
Tanaka, Miyako | Sakurai, Hidehiro
Changes in the ultraviolet absorption spectrum took place when coupling factor 1 of spinach chloroplasts (CF ₁) was mixed with ATP or ADP. The difference spectrum had a maximum at about 278 nm and a minimum at about 250 nm. The profile of the difference spectrum inidcates a shift in the absorption spectrum of the ADP or ATP bound to CF ₁. The ratio of the maximal absorbance change at about 278 nm to the absorbance of CF ₁ at that wavelength was 0.027–0.048. The molar concentration of nucleotide required to give the maximal absorbance change was 2–3 times that of CF ₁ when Ca ²⁻ or Mg ²⁺ was present. AMP induced no significant spectral change. When ADP was added, the absorbance change reached a plateau within a few minutes if Mg ²⁻ or Ca ²⁺ was present. The absorbance change induced by ATP reached a plateau within a few minutes only when Ca ²⁺ was present. In the presence of Mg ²⁺, it reached a plateau of nearly the same level, but at a slower rate. The absorbance change was reduced in the presence of EDTA. PPi effectively inhibited the absorbance change induced by ADP and Mg ²⁺.
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