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981.
982.
Reconstitution is one of the most fundamental and powerful tools to investigate pigment—protein complexes, for example, light-harvesting complexes and reaction center complexes. Two reconstitution methods, in vitro and in vivo, have been applied to complexes. In vitro reconstitution methods were first developed using isolated proteins and pigments, and recently using over-expressed proteins. This method enables analysis of pigment binding, pigment stoichiometry, and protein flexibility when accepting extrinsic pigments, however, it has not yet been successfully applied to the core antenna system. In vivo reconstitution, which was developed using genetic modifications, is applicable even on core systems. In this Review, the in vivo reconstitution is mainly considered on the basis of the in vitro reconstitution, because the former was a recent development and will be expanded to many systems. When genes for a new pigment are acquired and expressed, the new pigment is incorporated into a pre-exiting complex(es) and becomes functional when it is accepted by this complex(es), or abandoned if it is not. This process is postulated to occur during the evolutionary process(es) of antenna and reaction centers, and it is now possible to reproduce this evolutionary developmental pathway(s). Several examples of in vivo reconstitution are given and considered from the viewpoint of evolutionary implication with regards to the antenna and reaction centers.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献
983.
Yoshihiro Fuchikami Tohru Yoshimura Nobuyoshi Esaki 《Journal of Molecular Catalysis .B, Enzymatic》2003,23(2-6):321
-Amino acid aminotransferase (
-AAT) (EC 2.6.1.21) catalyzes the interconversion between various
-amino acids and α-keto acids. A subunit of the homodimeric enzyme from a thermophile, Bacillus sp. YM-1, consists of two distinct structural domains connected by one loop. We previously constructed an active fragmentary enzyme whose backbone was cut at the interdomain loop [J. Biochem. 124 (1998) 905]. In this work, we constructed 13 fragmentary
-amino acid aminotransferase genes by inserting a termination codon, an SD sequence, and an initiation codon into the specific positions of the gene corresponding to various loop regions and expressed in Escherichia coli cells. We have obtained six genes producing active fragmentary enzymes, one producing an inactive fragmentary enzyme, four producing only large peptide fragment, and another two that gave no products. The six active fragmentary enzymes purified to near-homogeneity showed various substrate specificities and thermostabilities distinct from each other and also from the wild-type enzyme: two exhibited higher catalytic activity towards
-alanine, the most efficient substrate, than the wild-type enzyme. These results suggest that cleavage at a loop region is an efficient method for the alteration of enzyme properties. 相似文献
984.
Martha M. Moore Masamitsu Honma Julie Clements George Bolcsfoldi Maria Cifone Robert Delongchamp Michael Fellows Bhaskar Gollapudi Peter Jenkinson Paul Kirby Stephan Kirchner Wolfgang Muster Brian Myhr Michael ODonovan Jo Oliver Takashi Omori Marie-Claude Ouldelhkim Kamala Pant Robert Preston Colin Riach Richard San Leon F. Stankowski Jr. Ajit Thakur Shinobu Wakuri Isao Yoshimura 《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》2003,540(2):127
The Mouse Lymphoma Assay (MLA) Workgroup of the International Workshop on Genotoxicity Tests (IWGT) met on June 28th and 29th, 2002, in Plymouth, England. This meeting of the MLA group was devoted to discussing the criteria for assay acceptance and appropriate approaches to data evaluation. Prior to the meeting, the group conducted an extensive analysis of data from both the microwell and soft agar versions of the assay. For the establishment of criteria for assay acceptance, 10 laboratories (6 using the microwell method and 4 using soft agar) provided data on their background mutant frequencies, plating efficiencies of the negative/vehicle control, cell suspension growth, and positive control mutant frequencies. Using the distribution curves generated from this data, the Workgroup reached consensus on the range of values that should be used to determine whether an individual experiment is acceptable. In order to establish appropriate approaches for data evaluation, the group used a number of statistical methods to evaluate approximately 400 experimental data sets from 10 laboratories entered into a database created for the earlier MLA Workshop held in New Orleans [Environ. Mol. Mutagen. 40 (2002) 292]. While the Workgroup could not, during this meeting, make a final recommendation for the evaluation of data, a general strategy was developed and the Workgroup members agreed to evaluate this new proposed approach using their own laboratory data. This evaluation should lead to a consensus global approach for data evaluation in the near future. 相似文献
985.
Tohru Suzuki Akira Ishikawa Takashi Yoshimura Takao Namikawa Hiroshi Abe Sato Honma Ken-ichi Honma Shizufumi Ebihara 《Mammalian genome》2001,12(4):272-277
CS mice show a free-running period (κ) longer than 24 h and rhythm splitting in constant darkness (DD). These features in
behavioral circadian rhythms are distinctive as compared with other inbred strains of mice, which exhibit robust free-running
rhythms with κ shorter than 24 h. To identify the genes affecting κ, quantitative trait locus (QTL) analysis was initially
conducted by using 289 F2 mice derived from a cross between CS and C57BL/6J strain. A suggestive QTL (LOD = 3.71) with CS allele increasing κ was detected
on the distal region of Chromosome (Chr) 19. Next, using 192 F2 mice from a cross between CS and MSM strain, the presence of the QTL on Chr 19 was examined, and we confirmed the QTL at
the genome-wide significant level (LOD = 4.61 with 10.4% of the total variance explained). This QTL was named long free-running
period (Lfp). Three other suggestive QTLs (LOD = 3.24–4.28) were mapped to the midportion of Chr 12 in (CS×C57BL/6J)F2 mice, and to the proximal and middle region of Chr 19 in (CS×MSM)F2 mice, respectively, of which, CS alleles for two QTLs on Chr 19 have the effect of lengthening κ. None of these QTLs were
mapped to the chromosomal regions of previously described QTLs for κ and known clock genes (Clock, mPer1, Bmal1, mCry1, mCry2, mTim, and Csnk1e).
Received: 5 July 2000 / Accepted: 5 December 2000 相似文献
986.
Overexpression of chlorophyllide a oxygenase (CAO) enlarges the antenna size of photosystem II in Arabidopsis thaliana 总被引:1,自引:0,他引:1
Ryouichi Tanaka Yoshihiro Koshino Shinichiro Sawa Sumie Ishiguro Kiyotaka Okada & Ayumi Tanaka 《The Plant journal : for cell and molecular biology》2001,26(4):365-373
The light-harvesting efficiency of a photosystem is thought to be largely dependent on its photosynthetic antenna size. It has been suggested that antenna size is controlled by the biosynthesis of chlorophyll b. To verify this hypothesis, we overexpressed the enzyme for chlorophyll b biosynthesis, chlorophyllide a oxygenase (CAO), in Arabidopsis thaliana by transforming the plant with cDNA for CAO under the control of the 35S cauliflower mosaic virus promoter. In the early de-etiolation phase, when the intrinsic CAO expression is very low, the chlorophyll a: b ratio was drastically decreased from 28 to 7.3, indicating that enhancement of chlorophyll b biosynthesis had been successfully achieved. We made the following observations in full-green rosette leaves of transgenic plants. (1) The chlorophyll a : b ratio was reduced from 2.85 to 2.65. (2) The ratio of the peripheral light-harvesting complexes (LHCII) to the core antenna complex (CPa) resolved with the green-gel system increased by 20%. (3) The ratio of the light-harvesting complex II apoproteins (LHCP) to 47-kDa chlorophyll a protein (CP47), which was estimated by the results of immunoblotting, increased by 40%. These results indicated that the antenna size increased by at least 10-20% in transgenic plants, suggesting that chlorophyll b biosynthesis controls antenna size. To the best of our knowledge, this is the first report on enlargement of the antenna size by genetic manipulations. 相似文献
987.
Interleukin-5 (IL-5) transgenic mice were used to assess the immunological features of CSF eosinophils from mice infected with Angiostrongylus cantonensis. CSF eosinophils were hypodense by day 14 post infection (p.i.). CSF eosinophils survived longer in vitro than peritoneal eosinophils collected from cadmium sulphate (CdSO4) -treated normal IL-5 transgenic mice. Apoptosis was measured by Annexin V binding and the presence of a distinct laddering pattern of DNA fragmentation on agarose electrophoresis. Regardless of the presence or absence of Actinomycin D, CSF eosinophils collected from IL-5 transgenic mice from days 15–36 p.i. exhibited less apoptosis than peritoneal eosinophils collected from uninfected IL-5 transgenic mice. CSF eosinophils collected from A. cantonensis infected C57BL/6 mice at days 15–34 p.i. showed elongation of survival time and less apoptosis during in vitro cultivation. Reduced apoptosis was noted only in CSF eosinophils, but not in peritoneal eosinophils recovered from the same infected IL-5 transgenic mice. CPP32/Caspase 3 activity of cultured peritoneal eosinophils from both infected and uninfected IL-5 transgenic mice was higher than that of cultured CSF eosinophils. Stimulation with A23187 readily induced apoptosis of peritoneal eosinophils, but not CSF eosinophils or peritoneal eosinophils cultured with mouse recombinant IL-5. The latter cells were morphologically identical to hypodense eosinophils. RT-PCR analysis indicated that bcl-2 and bcl-xL mRNA expression was higher in CSF eosinophils compared with peritoneal eosinophils and this expression in the latter cells was upregulated after culture with mouse recombinant IL-5. These results suggest that CSF eosinophils, shifting to hypodense status through an accumulation from peripheral blood, are resistant to apoptosis. These changes may explain the long-lasting, helminthotoxic and neurotoxic actions of CSF eosinophils in A. cantonensis infection. 相似文献
988.
M Yokouchi T Kondo A Sanjay A Houghton A Yoshimura S Komiya H Zhang R Baron 《The Journal of biological chemistry》2001,276(37):35185-35193
The protooncogene c-Cbl has recently emerged as an E3 ubiquitin ligase for activated receptor tyrosine kinases. We report here that c-Cbl also mediates the ubiquitination of another protooncogene, the non-receptor tyrosine kinase c-Src, as well as of itself. The c-Cbl-dependent ubiquitination of Src and c-Cbl requires c-Cbl's RING finger, Src kinase activity, and c-Cbl's tyrosine phosphorylation, probably on Tyr-371. In vitro, c-Cbl forms a stable complex with the ubiquitin-conjugating enzyme UbcH7, but active Src destabilizes this interaction. In contrast, Src inhibition stabilizes the c-Cbl. UbcH7.Src complex. Finally, c-Cbl reduces v-Src protein levels and suppresses v-Src-induced STAT3 activation. Thus, in addition to mediating the ubiquitination of activated receptor tyrosine kinases, c-Cbl also acts as a ubiquitin ligase for the non-receptor tyrosine kinase Src, thereby down-regulating Src. 相似文献
989.
Comparison of the genetic diversity of common wild rice (Oryza rufipogon Griff.) and cultivated rice (O. sativa L.) using RFLP markers 总被引:12,自引:0,他引:12
C. Q. Sun X. K. Wang Z. C. Li A. Yoshimura N. Iwata 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(1):157-162
Forty fourth single-copy RFLP markers were used to evaluate the genetic diversity of 122 accessions of common wild rice (CWR,
Oryza rufipogon Griff.) and 75 entries of cultivated rice (Oryza sativa L. ) from more than ten Asian countries. A comparison of the parameters showing genetic diversity, including the percentage
of polymorphic loci (P), the average number of alleles per locus (A), the number of genotypes (Ng), the average heterozygosity (Ho) and the average genetic multiplicity (Hs) of CWR and indica and japonica subspecies of cultivated rice from different countries and regions, indicated that CWR from China possesses the highest genetic
diversity, followed by CWR from South Asia and Southeast Asia. The genetic diversity of CWR from India is the second highest.
Although the average gene diversity (Hs)of the South Asian CWR is higher than that of the Southeast Asian CWR, its percentage of polymorphic loci (P), number of alleles (Na) and number of genotypes (Ng) are all smaller. It was also found that the genetic diversity of cultivated rice is obviously lower than that of CWR. At
the 44 loci investigated, the number of polymorphic loci of cultivated rice is only 3/4 that of CWR, while the number of alleles,
60%, and the number of genotypes is about 1/2 that of CWR. Of the two subspecies studied, the genetic diversity of indica is higher than that of japonica. The average heterozygosity of the Chinese CWR is the highest among all the entries studied. The average heterozygosity of
CWR is about two-times that of cultivated rice. It is suggested that during the course of evolution from wild rice to cultivated
rice, many alleles were lost through natural and human selection, leading to the lower heterozygosity and genetic diversity
of the cultivated rice.
Received: 19 May 1999 / Accepted: 26 April 2000 相似文献