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排序方式: 共有251条查询结果,搜索用时 46 毫秒
1.
Heterologous hybridization of ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) restores the enzyme activities 总被引:3,自引:0,他引:3
A Incharoensakdi T Takabe T Takabe T Akazawa 《Biochemical and biophysical research communications》1985,126(2):698-704
The catalytic core (A8) and small subunit (B) of ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) were isolated from two species of cyanobacteria (Aphanothece halophytica and Synechococcus ACMM 323) as well as from the photosynthetic purple sulfur bacterium, Chromatium vinosum. The subunit B is essential for the activity of all three enzymes. The heterologous hybridization of RuBisCO molecules from the three organisms was attempted and the reconstitution of the catalytically active hybrid was achieved between A8 derived from either Aphanothece or Synechococcus and subunit B from Aphanothece, Synechococcus or Chromatium. However, reconstitution of the enzymically active hybrid between A8 from Chromatium and B subunits from the cyanobacteria could not be achieved. Experiments by using high performance liquid column chromatography also showed the formation of a heterologous hybrid possessing RuBP carboxylase activity. 相似文献
2.
3.
Interaction of constituent subunits in ribulose 1,5-bisphosphate carboxylase from Aphanothece halophytica 总被引:3,自引:0,他引:3
Ribulose 1,5-bisphosphate carboxylase-oxygenase (RuBisCO) from the halophilic cyanobacterium, Aphanothece halophytica, dissociates into catalytic core (large subunit A oligomer) and small subunit B under low ionic strength during sucrose density gradient centrifugation. Supplementation of KCl, NaCl, or K2SO4 ( [I] = 0.3 M) partly prevents the dissociation, the preventive effect of divalent cation salts such as MgCl2 and CaCl2 being more effective than monovalent cation salts. RuBisCO with its higher-plant-type molecular form can be isolated from the cyanobacterial extracts using gradient medium containing 0.3 M KCl, 20 mM MgCl2, and 10 mM CaCl2. The isolated enzyme contains large subunit A and small subunit B in a molar ratio of approximately 1:1, estimated from the densitometric scanning of Coomassie blue-stained gels. During the second sucrose density gradient centrifugation to remove minor contaminants, a small amount of subunit B is depleted from the holoenzyme. Determination of the molecular weight by equilibrium centrifugation and electron microscopic observation have confirmed that the cyanobacterial RuBisCO has an A8B8-type structure. The enzyme activity per se is found to be sensitive to concentrations of salts, and small subunit B is obligatory for the enzyme catalysis. It has been shown that the more the enzyme activity is inhibited by salts, the tighter the association of subunit B becomes. It is likely that the active enzyme retains the loose conformational structure to such an extent that the dissociable release of subunit B from the holoenzyme in vivo is not allowed. 相似文献
4.
Compression wood (CW) contains higher quantities of β-1-4-galactan than does normal wood (NW). However, the physiological
roles and ultrastructural distribution of β-1-4-galactan during CW formation are still not well understood. The present work
investigated deposition of β-1-4-galactan in differentiating tracheids of Cryptomeria japonica during CW formation using an immunological probe (LM5) combined with immunomicroscopy. Our immunolabeling studies clearly
showed that differences in the distribution of β-1-4-galactan between NW (and opposite wood, OW) and CW are initiated during
the formation of the S1 layer. At this stage, CW was strongly labeled in the S1 layer, whereas no label was observed in the S1 layer of NW and OW. Immunogold labeling showed that β-1-4-galactan in the S1 layer of CW tracheids significantly decreased during the formation of the S2 layer. Most β-1-4-galactan labeling was present in the outer S2 region in mature CW tracheids, and was absent in the inner S2 layer that contained helical cavities in the cell wall. In addition, delignified CW tracheids showed significantly more labeling
of β-1-4-galactan in the secondary cell wall, suggesting that lignin is likely to mask β-1-4-galactan epitopes. The study
clearly showed that β-1-4-galactan in CW was mainly deposited in the outer portion of the secondary cell wall, indicating
that its distribution may be spatially consistent with lignin distribution in CW tracheids of Cryptomeria japonica. 相似文献
5.
Summary Growing pollen tubes of tobacco germinated in suspension culture, were labelled with [3H]leucine and after varying times of chase with unlabelled leucine at 23, 16, or 4°C, were separated into plasma membrane-enriched and plasma membrane-depleted fractions by aqueous two-phase partition. At 23°C, the specific radioactivity of the plasma membrane increased with time to a maximum at 60 min. At 16°C and 4°C, labelling of the plasma membrane was respectively 40% and 10% that at 23°C. However, if labelling was at 23°C and subsequent transfer was at 4°C, plasma membrane labelling was much less affected and labelling of the plasma membrane was 60% that at 23°C. Additionally, quantitation of various morphological parameters revealed no accumulations of 50–70 nm transition vesicles in the space between endoplasmic reticulum and cis Golgi apparatus that might suggest formation of a low temperature compartment similar to those described for mammalian cells and tissues. Similarly, growth of pollen tubes was reduced but not blocked even at temperatures of 12°C. The results suggest that tube elongation is accompanied by a steady state flow of membranes to the cell surface that is relatively insensitive to interruption by low temperatures. Whereas leucine incorporation is reduced by low temperature even at 16°C, the flow pathway to the cell surface, including the endoplasmic reticulum to Golgi apparatus transfer step, as well as elongation growth does not exhibit a pronounced low temperature block in this tip growing system. 相似文献
6.
Gong Chang Cheng Ziliang Yang Yaping Shen Jun Zhu Yingying Ling Li Lin Wanyi Yu Zhigang Li Zhihua Tan Weige Zheng Chushan Zheng Wenbo Zhong Jiajie Zhang Xiang Zeng Yunjie Liu Qiang Huang R. Stephanie Komorowski Andrzej L. Yang Eddy S. Bertucci François Ricci Francesco Orlandi Armando Franceschini Gianluca Takabe Kazuaki Klimberg Suzanne Ishii Naohiro Toss Angela Tan Mona P. Cherian Mathew A. Song Erwei 《中国科学:生命科学英文版》2022,65(11):2205-2217
Science China Life Sciences - Patients with hormone receptor (HR)-positive tumors breast cancer usually experience a relatively low pathological complete response (pCR) to neoadjuvant chemotherapy... 相似文献
7.
8.
Yukiko Yamada Tatsuya Awano Minoru Fujita Keiji Takabe 《Trees - Structure and Function》2011,25(4):607-616
A living wood fiber (LWF) is one that retains the living protoplast. LWFs store numerous starch grains during the dormant
period. In black locust (Robinia pseudoacacia), almost all wood fibers in the outer part of the annual ring are LWFs. In the outermost ring, starch is accumulated during
the summer, retained in winter, and metabolized during spring. We determined the starch content of LWFs, ray parenchyma, and
axial parenchyma using image analysis. More than 70% of the starch grains in the outermost ring were stored in LWFs during
winter. After the breakdown of starch in spring, LWFs resulted in cell death. These results indicate that LWFs in black locust
function as “single-use” large-capacity starch storage. 相似文献
9.
Yusuke Sekiguchi Tetsuko Nakaniwa Takayoshi Kinoshita Isao Nakanishi Kazuo Kitaura Akira Hirasawa Gozoh Tsujimoto Toshiji Tada 《Bioorganic & medicinal chemistry letters》2009,19(11):2920-2923
We determined the 2.35-Å crystal structure of a human CK2 catalytic subunit (referred to as CK2α complexed with the ATP-competitive, potent CK2 inhibitor ellagic acid. The inhibitor binds to CK2α with a novel binding mode, including water-mediated hydrogen bonds. This structural information may support discovery of potent CK2 inhibitors. 相似文献
10.
Tetsuko Takabe Mikio Nishimtjra Takashi Akazawa 《Bioscience, biotechnology, and biochemistry》2013,77(10):2137-2142
The isolation of the photosynthetically competent chloroplast preparations was undertaken by means of the density gradient centrifugation on the modified silica sol “Percoll.” A clear separation of the intact chloroplast sustaining the high photosynthetic activities (light dependent CO2 fixation ca. 130μmol/mg Chl·hr) was established. The contamination of mitochondria and peroxisomes was estimated to be less than 3% by measuring the activities of their marker enzymes. The chloroplasts were proved to be free from endoplasmic reticulum and cytosol. The photosynthetic CO2 fixation of the isolated chloroplast preparations was saturated by illumination of the light intensity of 20,000 Lux (12 mW/cm2, 400~750 nm). 相似文献