Inhibition of plastocyanin to P(700)(+) electron transfer in Chlamydomonas reinhardtii by hyperosmotic stress.
Oxygen electrode and fluorescence studies demonstrate that linear electron transport in the freshwater alga Chlamydomonas reinhardtii can be completely abolished by abrupt hyperosmotic shock. We show that the most likely primary site of inhibition of electron transfer by hyperosmotic shock is a blockage of electron transfer between plastocyanin (PC) or cytochrome c(6) and P(700). The effects on this reaction were reversible upon dilution of the osmolytes and the stability of plastocyanin or photosystem (PS) I was unaffected. Electron micrographs of osmotically shocked cells showed a significant decrease in the thylakoid lumen volume. Comparison of estimated lumenal width with the x-ray structures of plastocyanin and PS I suggest that lumenal space contracts during HOS so as to hinder the movement of docking to PS I of plastocyanin or cytochrome c(6).
Cruz
J A
JA
Institute of Biological Chemistry, Department of Biochemistry and Biophysics, 289 Clark Hall, Washington State University, Pullman, WA 99164-6340, USA.
Salbilla
B A
BA
Kanazawa
A
A
Kramer
D M
DM
D000818:Animals; D002241:Carbohydrates / Q000494:pharmacology; D016825:Chlamydomonas reinhardtii / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002734:Chlorophyll / Q000378:metabolism* / Q000493:pharmacokinetics / Q000528:radiation effects; D000077194:Chlorophyll A; D003580:Cytochromes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D045348:Cytochromes f; D004579:Electron Transport / Q000187:drug effects / Q000528:radiation effects; D005453:Fluorescence; D008027:Light; D045342:Light-Harvesting Protein Complexes; D009997:Osmotic Pressure; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects / Q000528:radiation effects; D010970:Plastocyanin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012492:Salts / Q000494:pharmacology; D020524:Thylakoids / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure
D002241:Carbohydrates; D003580:Cytochromes; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D012492:Salts; D002734:Chlorophyll; C001785:chlorophyll P 700; D010970:Plastocyanin; D045348:Cytochromes f; D010100:Oxygen; D000077194:Chlorophyll A