Springer Online Journal Archives 1860-2000
Abstract Several eukaryotic algae belonging to the main taxonomic classes have been cultured autotrophically in liquid medium supplemented with or depleted of copper to assay their ability to form plastocyanin or exchange it against plastidic cytochrome c-553. Most Chlorophyceae are able to substitute cytochrome c-533 for plastocyanin with some exceptions like Haematococcus or Dunaliella, which can only synthesize plastocyanin. Also within the Chlorella group, about half of the 28 strains assayed cannot synthesize cytochrome c-553 under copper deficiency. Species of Chrysophyceae, Xanthophyceae, and Rhodophyceae, on the other hand, cannot synthesize plastocyanin even when a comparatively high copper concentration (10μM) is available. Serological cross-reactions of various plastocyanincontaining Chlorella homogenates against an antibody towards Scenedesmus plastocyanin exhibit a pattern which cannot be taxonomically used at the moment. Including previous data on blue-green algae, it appears that, in the course of evolution, cytochrome c-553 dominates in the older species. In the Chlorophyceae, it is mutually exchangeable against plastocyanin which becomes the only electron donor to P700 in higher plants.
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