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Plant and Cell Physiology, 1973, Vol. 14, No. 1 61-75
© 1973

Article

Anion-dependent changes of energy transfer in chloroplasts I. Effects of Tris salts on electron flow and phosphorylation

Norikatsu Ikehara1 and Mitsuo Nishimura

Department of Biology, Faculty of Science, Kyushu University Fukuoka 812, Japan

Washing spinach chloroplasts with high-concentration Tris-salt buffers induced various types of anion-dependent changes in the electron flow and photophosphorylation in chloroplasts.

Tris-HCl buffer caused enhancement of NADP photoreduction and inhibition of phosphorylation. Tris-HNO3 buffer, on the other hand, caused inhibition of both electron flow and phosphorylation and decreased trypsin-activated Ca2+-dependent ATPase activity. Tris-H2SO4 and Tris-H3PO4 buffers, however, had no effect on the rates of electron flow and photophosphorylation.

Determination of the presence of the coupling factor (as measured by ATPase activity) revealed a normal enzyme activity level in chloroplasts washed with Tris-HCl or Tris-H2SO4 buffer. Removal of the coupling factor by EDTA from chloroplasts washed with Tris salts inhibited phosphorylation severely. Phosphorylation activity could be partially restored by reconstitution with the coupling factor in die presence of Mg2+.

In addition to their different effects on electron flow, Tris-HCl and Tris-HNO3 induced a marked decrease in phosphorylative activity itself. The much decreased rate of phosphorylation can be explained by the release of the coupling factor and by damage to the high-energy state generating mechanism by Tris-HNO3-washing and by modification of the coupling factor in the case of Tris-HCl-washing.

1Present address: Biology Department, College of Science and Engineering, Ryukyu University, Naha, Okinawa. Japan.

(Received June 27, 1972; )
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