title: Decrease in the efficiency of the electron donation to tyrosine Z of photosystem II in an SQDG-deficient mutant of Chlamydomonas.
abstract: Photosystem (PS) II activity of a sulfoquinovosyl diacylglycerol (SQDG)-deficient mutant (hf-2) of Chlamydomonas was partially decreased compared with that of wild-type. The susceptibility to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) was also modified in the mutant. Photometric measurements in the isolated thylakoid membranes of hf-2 revealed that the lowered activity in the mutant was derived from a decrease in the efficiency of the electron donation from water to tyrosine Z, not from the efficiency of the electron transport from Q(A) to Q(B). This result was confirmed by the decay kinetics of chlorophyll fluorescence determined in vivo. We conclude that SQDG contributes to maintaining the conformation of PSII complexes, particularly that of D1 polypeptides, which are necessary for maximum activities in Chlamydomonas.
authors.affiliation: School of Life Science, Tokyo University of Pharmacy and Life Science, Horinouchi, Hachioji, Tokyo, Japan. aa17115@mail.ecc.u-tokyo.ac.jp
authors.forename: Ayumi
authors.initials: A
authors.lastname: Minoda
authors.forename: Kintake
authors.initials: K
authors.lastname: Sonoike
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Okada
authors.forename: Norihiro
authors.initials: N
authors.lastname: Sato
authors.forename: Mikio
authors.initials: M
authors.lastname: Tsuzuki
mesh_terms: D064753:Ammonium Hydroxide; D000818:Animals; D002696:Chlamydomonas / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport / Q000187:drug effects; D006207:Half-Life; D006878:Hydroxides / Q000494:pharmacology; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes; D009154:Mutation / Q000235:genetics*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D013050:Spectrometry, Fluorescence; D020524:Thylakoids / Q000187:drug effects / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D006878:Hydroxides; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D014443:Tyrosine; D064753:Ammonium Hydroxide