Mechanism of Cd2+ toxicity: Cd2+ inhibits photoactivation of Photosystem II by competitive binding to the essential Ca2+ site. Export

@article{citeulike:562509, abstract = {Cadmium (Cd2+) is a well-known highly toxic element. The molecular mechanisms of the Cd2+ toxicity are not well understood. In photosynthetic organisms, toxic Cd2+ concentrations are often in the low-microM range. It has been proposed that low-microM Cd2+ concentrations affect photosynthesis at the level of Photosystem II by inhibiting oxygen evolution. However, in vitro studies on isolated, functional Photosystem II showed that much higher Cd2+ concentrations (mM range) were needed for inhibition. Here we show that Cd2+ in the low-microM range inhibited photoactivation (i.e., assembly of the water splitting complex) in Chlamydomonas reinhardtii and in isolated Photosystem II. Photoactivation is the last step in the assembly of Photosystem II before it becomes functional. The exact Cd2+ concentration necessary for inhibition depended on the concentration of calcium. It is proposed that Cd2+ binds competitively to the essential Ca2+ site in Photosystem II during photoactivation. The low Cd2+ concentration needed to inhibit photoactivation suggests that this event is also involved in the Cd2+-induced inhibition of photosynthesis in vivo. This mechanism is likely to be important for Cd2+ toxicity towards photosynthetic organisms in general, at least in unicellular like C. reinhardtii where Cd2+ has easy access to the photosynthetic apparatus.}, address = {Institut f\"{u}r Biologie II, Biochemie der Pflanzen, Universit\"{a}t Freiburg, Sch\"{a}nzlestr. 1, 79104 Freiburg, Germany.}, author = {Faller, P. and Kienzler, K. and Krieger-Liszkay, A.}, citeulike-article-id = {562509}, citeulike-linkout-0 = {http://dx.doi.org/10.1016/j.bbabio.2004.10.005}, citeulike-linkout-1 = {http://view.ncbi.nlm.nih.gov/pubmed/15620376}, citeulike-linkout-2 = {http://www.hubmed.org/display.cgi?uids=15620376}, day = {7}, doi = {10.1016/j.bbabio.2004.10.005}, issn = {0006-3002}, journal = {Biochim Biophys Acta}, keywords = {cadmium, calcium, oec, oec\_ca\_site, psii, psii\_inhibitors}, month = {January}, number = {1-2}, pages = {158--164}, posted-at = {2006-03-24 14:52:10}, priority = {5}, title = {Mechanism of Cd2+ toxicity: Cd2+ inhibits photoactivation of Photosystem II by competitive binding to the essential Ca2+ site.}, url = {http://dx.doi.org/10.1016/j.bbabio.2004.10.005}, volume = {1706}, year = {2005} }

TY - JOUR ID - citeulike:562509 L3 - citeulike-article-id:562509 N2 - Cadmium (Cd2+) is a well-known highly toxic element. The molecular mechanisms of the Cd2+ toxicity are not well understood. In photosynthetic organisms, toxic Cd2+ concentrations are often in the low-microM range. It has been proposed that low-microM Cd2+ concentrations affect photosynthesis at the level of Photosystem II by inhibiting oxygen evolution. However, in vitro studies on isolated, functional Photosystem II showed that much higher Cd2+ concentrations (mM range) were needed for inhibition. Here we show that Cd2+ in the low-microM range inhibited photoactivation (i.e., assembly of the water splitting complex) in Chlamydomonas reinhardtii and in isolated Photosystem II. Photoactivation is the last step in the assembly of Photosystem II before it becomes functional. The exact Cd2+ concentration necessary for inhibition depended on the concentration of calcium. It is proposed that Cd2+ binds competitively to the essential Ca2+ site in Photosystem II during photoactivation. The low Cd2+ concentration needed to inhibit photoactivation suggests that this event is also involved in the Cd2+-induced inhibition of photosynthesis in vivo. This mechanism is likely to be important for Cd2+ toxicity towards photosynthetic organisms in general, at least in unicellular like C. reinhardtii where Cd2+ has easy access to the photosynthetic apparatus. IS - 1-2 JF - Biochim Biophys Acta SN - 0006-3002 AD - Institut für Biologie II, Biochemie der Pflanzen, Universität Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany. EP - 164 TI - Mechanism of Cd2+ toxicity: Cd2+ inhibits photoactivation of Photosystem II by competitive binding to the essential Ca2+ site. VL - 1706 SP - 158 KW - cadmium KW - calcium KW - oec KW - oec_ca_site KW - psii KW - psii_inhibitors AU - Faller, P AU - Kienzler, K AU - Krieger-Liszkay, A PY - 2005/01/07/ UR - http://dx.doi.org/10.1016/j.bbabio.2004.10.005 ER -