SUBCELLULAR-DISTRIBUTION OF CADMIUM IN THE UNICELLULAR GREEN-ALGA CHLAMYDOMONAS-REINHARDTII

As previously reported, cadmium strongly inhibits photosynthesis in th e unicellular green alga Chlamydomonas reinhardtii. A cadmium-tolerant mutant with impaired photosynthesis has been isolated recently. There fore, we have investigated tile subcellular distribution of Cd-109(2+) in the cell-wall deficient C. reinhardtii mutant strain CW15. The cyt osol only contained about 10% of the incorporated Cd-109(2+). The pred ominant proportion of Cd2+, however was found in the purified chloropl asts (more than 50%), although a considerable part of the chloroplasts was destroyed during the disrupture of the cells. Fractionation of (p oly)peptide-bound and free Cd-109(2+) by Sephadex G75 chromatography r evealed essentially the same distribution for the lysates of purified chloroplasts as for the cytosol. A considerable proportion of the inco rporated Cd-109(2+) was sequestered by complex formation with oligopep tides both in the cytosol and in the chloroplasts.