Showing papers by "Jun Minagawa published in 1999"
TL;DR: It is concluded that equilibrium constants for sharing an electron between the primary (QA) and secondary acceptor plastoquinones (QB) are decreased in both mutants.
Abstract: Several random mutations have been generated in the psbA2 gene of Synechocystis sp PCC 6803 [Narusaka, Y, Murakami, A, Saeki, J, Kobayashi, H, and Satoh, K (1996) Plant Sci 115, 261-266] The phototolerant mutant (I6) carrying all the amino acid substitutions in the lumenal side of D1 protein (S322I, I326F, and F328S) and a site-directed mutant of the same phenotype (NDFS) substituted in the stromal side of the protein (N234D and F260S) were characterized by thermoluminescence measurements We observed (1) no significant differences in their growth rates at either low or high light irradiance, (2) a downshifted B-band in the NDFS mutant, (3) an upshifted Q-band in the I6 mutant, and (4) a damped period four oscillation of thermoluminescence in the B-band of both mutants By examining the possible implications of these results on the redox properties of the PS II components in the mutants, we concluded that equilibrium constants for sharing an electron between the primary (QA) and secondary acceptor plastoquinones (QB) are decreased in both mutants
38 citations
TL;DR: It was inferred from results that His-tagging at the C-terminus of the D2 protein does not affect the functional and structural integrity of the PSII core complex, and that the 'His-tag strategy' is highly useful for biochemical, physicochemical, and structural studies of Chlamydomonas PSII.
Abstract: A His-tagged PSII core complex was purified from recombinant Chlamydomonas reinhardtii D2-H thylakoids by single-step Ni2+-affinity column chromatography and its properties were partially characterized in terms of their PSII functions and chemical compositions. The PSII core complex that has a His-tag extension at the C-terminus of the D2 protein evolved oxygen at a high rate of 2,400 ^mol (mg Chi)"1 h"1 at the optimum pH of 6.5 with ferricyanide and 2,6-dichlorobenzoquinone as electron acceptors in the presence of Ca 2+ as an essential cofactor, and approximately 90% of the activity was blocked by 10 /M DCMU. The core complex exhibited the thermoluminescence Q-band but not the B-band regardless of the presence or absence of DCMU, although both bands were observed in the His-tagged thylakoids. The core complex was free from PSI and contained one YD, Tyr 160 of the D2 protein, four Mn atoms, two cytochrome b-559, about 46 Chi a molecules, and probably one QA, the primary acceptor quinone of PSII. It was inferred from these results that His-tagging at the C-terminus of the D2 protein does not affect the functional and structural integrity of the PSII core complex, and that the 'His-tag strategy' is highly useful for biochemical, physicochemical, and structural studies of Chlamydomonas PSII.
14 citations