Photosynthetic phosphorylation in mitochondria-free chloroplast suspensions from leaves of Vicia faba L.

Abstract

Chloroplast were prepared from leaves of Vicia faba L. Electron micrographs showed that crude chloroplast suspensions prepared by the classical differential centrifugation procedure were contaminated by mitochondria: the mitochondria were completely removed by a further centrifugation of the crude chloroplast preparations through a glycerol-sucrose density gradient. Most of the chloroplast in the crude preparations and all the chloroplast after centrifugation through the density gradient were devoid of external membranes and stroma.The mitochondria-free chloroplast suspensions were able to mediate photo-phosphorylation with 3·10−5 M FMN and 10−4 M vitamin K3 as co-factors. The rate of photophosphorylation, the product (ATP) and the nonadditive effect of the co-factors compare closely with the results of other workers who used spinach chloroplasts prepared by differential centrifugation alone.Thus, photphosphorylation would appear to be a real aspect of the metabolism of isolated chloroplast; mitochondria are not involved in the process.