The Syntheses of Plastocyanin and Cytochrome c-553 Are Regulated by Copper at the Pre-Translational Level in a Green Alga, Pediastrum boryanum

Publisher Website
Google Scholar
Abstract
The green alga Pediastrwn boryanum synthesizes alternatively two photosynthetic electron carrier proteins, plastocyanin and cytochrome c-553, depending on the copper concentration of the medium. We studied the levels at which the syntheses of the two proteins are regulated. Plastocyanin and cytochrome c-553 were purified from P. boryanum MES-301 cells, having apparent molecular weights of 14,600 and about 12,000, respectively. Western blotting with antisera raised against these proteins showed accumulation of (apo)plastocyanin and (apo)cytochrome c-553 in the cells grown with (2 μM) and without added CuSO4, respectively, but no accumulation of the precursor proteins In both cultures. The translatable mRNAs for the two proteins were examined by in vitro translation with total RNA and wheat germ extract followed by immunoprecipitation and SDS-PAGE. The 21-kDa polypeptide (preapoplastocyanin) was detected with anti-plastocyanin serum in copper-sufficient cells; the 23-kfla polypeptlde (preapocytochrome c-553) with anti-cytochrome c-553 serum in copper-deficient cells. The translatable mRNA for preapoplastocyanin appeared in 1 h and (apo)plastocyanin in 2–3 h after the addition of 2 μM CuSO4 to the copper-deficient culture. The translatable mRNA for preapocytochrome c-553 disappeared within 4–5 h, while (apo)cytochrome c-553 disappeared more slowly. It Is concluded that the syntheses of plastocyanin and cytochrome c-553 are regulated by copper at the pre-translational (i.e., transcriptional or post-transcriptional) level in P. boryanum NIES-301.

This publication has 0 references indexed in Scilit: