It has been known that arginine is used as the basic amino acid in the α-subunit of cytochrome bsss （Cyt bsss） except histidine. However, previous studies have focused on the function of histidine in the activities...It has been known that arginine is used as the basic amino acid in the α-subunit of cytochrome bsss （Cyt bsss） except histidine. However, previous studies have focused on the function of histidine in the activities of photosystem （PS） Ⅱ and there are no reports regarding the structural and/or functional roles of arginine in PSll complexes. In the present study, two arginine18 （R18） mutants of Chlamydomonas reinhardtii were constructed using site-directed mutagenesis, in which R18 was replaced by glutamic acid （E） and glycine （G）. The results show that the oxygen evolution of the PSII complex in the R18G and R18E mutants was approximately 60% of wild-type （WT） levels and that, after irradiation at high light intensity, oxygen evolution for the PSll of mutants was reduced to zero compared with 40% in WT cells. The efficiency of light capture by PSll （Fv/Fm） of R18G and R18E mutants was approximately 42%-46% that of WT cells. Furthermore, levels of the α-subunit of Cyt bsss and PsbO proteins were reduced in thylakoid membranes compared with WT. Overall, these data suggest that R18 plays a significant role in helping Cyt bss9 maintain the structure of the PSll complex and its activity, although it is not directly bound to the heme group.展开更多
In order to elucidate the phylogenetic relationship of fish, DNA and deduced amino acid sequences of myoglobin （Mb） were used for the phylogenetic analyses based on different approaches, namely, maximum likelihood ...In order to elucidate the phylogenetic relationship of fish, DNA and deduced amino acid sequences of myoglobin （Mb） were used for the phylogenetic analyses based on different approaches, namely, maximum likelihood （ML）, neighbor joining （NJ）, unweighted pair group method with arithmetic means （UPGMA） and maximum parsimony （MP） methods in comparison with the conventional molecular markers, mitochondrial cytochrome b （cyt-b） and cytochrome c oxidase subunit I （COI）. The phylogenetic trees drawn based on Mb sequences were similar to those by the traditional classification based on the other molecular markers. The primary and secondary structures, as well as the modeled tertiary structures of Mbs were similar to each other, but were clearly distinguishable among those species. Such differences in structure would be associated with adaptation of Mb molecule to the physiological conditions of each species. These results suggest that Mb can be a molecular marker for the phylogenetic relationship of fish.展开更多
Mossbauer spectrum measured for the iron components of photosystem Ⅱ (PS Ⅱ ) particles of spinach is a superposition of 4 doublets. Quadrupole splitting and chemical shifting of doublets I -IV are characteris-tics o...Mossbauer spectrum measured for the iron components of photosystem Ⅱ (PS Ⅱ ) particles of spinach is a superposition of 4 doublets. Quadrupole splitting and chemical shifting of doublets I -IV are characteris-tics of proteins with oxidized cytochrome b-559, reduced cytochrome b-559, Fe3 + -Q complex and Fe2+ -Q complex re-spectively . After the PS II particles are treated with La3+ , two doublets of Fe2+ disappear and Fe2+ is converted into Fe3+ , indicating that the reduced cytochrome b-559 has been converted into the oxidized cytochrome b-559, and Fe2+-Q complex into Fe3+-Q complex. The Mossbauer spectrum of PS II particles treated with La3+ and Ca2+ shows that Ca2+ can weaken the inhibitory effect of La3+ in part, and a portion of the reduced cytochrome b-559 and Fe-Q complex still exist.展开更多
基金Supported by the National Natural Science Foundation of China （30370849）.The authors thank EH Harris （Duke University, Durham, NC, USA） for the gift of C. reinhardtii WT strain CC-125 mt^＋, plasmid p78 and pUC-atpX-AAD. Antiserum for the α-subunit of Cyt b559 was kindly provided by J Barber （Imperial College of Science, Technology and Medicine, London, UK）, and anti-Psb0 and anti-LHCII were provided by Li-Xin Zhang （Institute of Botany, Chinese Academy of Sciences, Beijing, China）.
文摘It has been known that arginine is used as the basic amino acid in the α-subunit of cytochrome bsss （Cyt bsss） except histidine. However, previous studies have focused on the function of histidine in the activities of photosystem （PS） Ⅱ and there are no reports regarding the structural and/or functional roles of arginine in PSll complexes. In the present study, two arginine18 （R18） mutants of Chlamydomonas reinhardtii were constructed using site-directed mutagenesis, in which R18 was replaced by glutamic acid （E） and glycine （G）. The results show that the oxygen evolution of the PSII complex in the R18G and R18E mutants was approximately 60% of wild-type （WT） levels and that, after irradiation at high light intensity, oxygen evolution for the PSll of mutants was reduced to zero compared with 40% in WT cells. The efficiency of light capture by PSll （Fv/Fm） of R18G and R18E mutants was approximately 42%-46% that of WT cells. Furthermore, levels of the α-subunit of Cyt bsss and PsbO proteins were reduced in thylakoid membranes compared with WT. Overall, these data suggest that R18 plays a significant role in helping Cyt bss9 maintain the structure of the PSll complex and its activity, although it is not directly bound to the heme group.
文摘In order to elucidate the phylogenetic relationship of fish, DNA and deduced amino acid sequences of myoglobin （Mb） were used for the phylogenetic analyses based on different approaches, namely, maximum likelihood （ML）, neighbor joining （NJ）, unweighted pair group method with arithmetic means （UPGMA） and maximum parsimony （MP） methods in comparison with the conventional molecular markers, mitochondrial cytochrome b （cyt-b） and cytochrome c oxidase subunit I （COI）. The phylogenetic trees drawn based on Mb sequences were similar to those by the traditional classification based on the other molecular markers. The primary and secondary structures, as well as the modeled tertiary structures of Mbs were similar to each other, but were clearly distinguishable among those species. Such differences in structure would be associated with adaptation of Mb molecule to the physiological conditions of each species. These results suggest that Mb can be a molecular marker for the phylogenetic relationship of fish.
基金Project supported by the National Natural Science Foundation of China and the Natural Science Foundation of the Chinese Educational Commission.
文摘Mossbauer spectrum measured for the iron components of photosystem Ⅱ (PS Ⅱ ) particles of spinach is a superposition of 4 doublets. Quadrupole splitting and chemical shifting of doublets I -IV are characteris-tics of proteins with oxidized cytochrome b-559, reduced cytochrome b-559, Fe3 + -Q complex and Fe2+ -Q complex re-spectively . After the PS II particles are treated with La3+ , two doublets of Fe2+ disappear and Fe2+ is converted into Fe3+ , indicating that the reduced cytochrome b-559 has been converted into the oxidized cytochrome b-559, and Fe2+-Q complex into Fe3+-Q complex. The Mossbauer spectrum of PS II particles treated with La3+ and Ca2+ shows that Ca2+ can weaken the inhibitory effect of La3+ in part, and a portion of the reduced cytochrome b-559 and Fe-Q complex still exist.
