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991.
Recent years have seen the convergence of both genetic and biochemical approaches in the study of protein translocation inE. coli. The powerful combination of these approaches is exemplified in the use of anin vitro protein synthesis-protein translocaltion system to analyze the role of genetically defined components of the protein translocation machinery. We describe in this review recent results focusing on the function of thesecA, secB, andsecY gene products and the demonstration of their requirement forin vitro protein translocation. The SecA protein was recently shown to possess ATPase activity and was proposed to be a component of the translocation ATPase. We present a speculative working model whereby the translocator complex is composed of the integral membrane proteins SecY, SecD, SecE, and SecF, forming an aqueous channel in the cytoplasmic membrane, and the tightly associated peripheral membrane protein SecA functioning as the catalytic subunit of the translocator or protein-ATPase. 相似文献
992.
Gerhard Sandmann M. Luisa Peleato Maria F. Fillat M. Carmen Lázaro Carlos Gómez-Moreno 《Photosynthesis research》1990,26(2):119-125
Iron-dependent formation of ferredoxin and flavodoxin was determined in Anabaena ATCC 29413 and ATCC 29211 by a FPLC procedure. In the first species ferredoxin is replaced by flavodoxin at low iron levels in the vegetative cells only. In the heterocysts from Anabaena ATCC 29151, however, flavodoxin is constitutively formed regardless of the iron supply.Replacement of ferredoxin by flavodoxin had no effect on photosynthetic electron transport, whereas nitrogen fixation was decreased under low iron conditions. As ferredoxin and flavodoxin exhibited the same Km values as electron donors to nitrogenase, an iron-limited synthesis of active nitrogenase was assumed as the reason for inhibited nitrogen fixation. Anabaena ATCC 29211 generally lacks the potential to synthesize flavodoxin. Under iron-starvation conditions, ferredoxin synthesis is limited, with a negative effect on photosynthetic oxygen evolution. 相似文献
993.
Yuan Han-min V. D. Keppenne P. S. Baenziger T. Berke G. H. Liang 《Plant Cell, Tissue and Organ Culture》1990,21(3):253-258
Four winter wheat (Triticum aestivum L.) and two spring wheat cultivars were evaluated in anther culture on three to four different media for their ability to initiate callus and green plants. Five media were used in the experiment: stored-potato medium with Ficoll 400, fresh-potato medium with Ficoll 400, fresh-potato medium with agar, fresh-potato liquid medium without agar or Ficoll 400, and a one tep 85D12-3 medium. Greatly different frequencies of calli and/or green plants were obtained from different cultivars and media. The callus initiation frequency varied from 2.7% for Arapahoe to 52% for Pavon, both on the stored potato medium with Ficoll 400. The frequency of green plant regeneration ranged from 0% for Arapahoe and Siouxland on the stored-potato medium with Ficoll 400 and 0% for Redland and Arapahoe in the fresh-potato medium with Ficoll 400 to 12% for Chris in the 85D12-3 medium (one-step procedure). Chris and Centurk 78, previously reported as having high levels of response, had significantly higher (P < 0.05) frequencies of green plant regeneration on the 851312-3 medium than the other cultivars. An unexpected observation is that wet MSC– medium enhanced callus regeneration more than a drier MSC– medium. 相似文献
994.
995.
Characterization of human autoantibodies specific for lamin A 总被引:2,自引:0,他引:2
J C Courvalin N Chaudhary F Danon J C Brouet K Lassoued 《Biology of the cell / under the auspices of the European Cell Biology Organization》1990,69(2):93-97
We have characterized human autoimmune polyclonal antibodies reactive with lamin A, a 74 kDa peripheral protein of the nuclear envelope. Unlike other known antibodies to lamin A, the antibodies described here do not crossreact with the structurally related lamin C. These antibodies feature only chi light chains suggesting that their specificity is restricted to a limited number of epitopes. Based on the known amino acid sequence of human lamins A and C, the epitope(s) are most likely located in the 80 amino acid carboxyl tail of mature lamin A. 相似文献
996.
The genomic organization and chromosomal location of theβ-tubulin isogenes inLeishmania donovani promastigotes has been studied by nucleic acid hybridization techniques using a cloned β-tubulin gene. We have cloned aβ-tubulin gene fragment, 3.3 kbp long, from genomic DNA ofLeishmania donovani using a heterologousβ-tubulin DNA as probe. Restriction maps of this clone have been prepared. It has been estimated that there are approximately
11–15 copies of theβ-tubulin genes per haploid genome. The majority of these isogenes are arranged in a tandem repeat with a length of 3.5 kbp
on a single chromosome. In addition a few dispersed gene copies at different chromosomal loci were detected by pulse field
gradient gel electrophoresis. Part of the internal coding region of the gene has been sequenced to confirm the identity of
theβ-tubulin clone and is found to be nearly identical to that ofLeishmania mexicana amazonensis. 相似文献
997.
V. S. Gupta M. S. Dhar B. G. Patil G. S. Narvekar S. R. Ra Wat P. K. Ranjekar 《Journal of biosciences》1990,15(4):261-269
Rice long repetitive DNA (9–20 kbp) reassociating at Cot 50 M.s was cloned in pBR325. Out of several recombinants (Camr Ampr Tets), only a few were selected randomly for further characterization. The insert size in all these clones was 3–4 kbp. Restriction
enzyme analysis showed the absence ofEcoRI andBclI sites, presence of a singlePstI andPvuII site and multiple sites forAluI in 3 clones namely pRLl, pRL7 and pRL10.
TheBamHI-PstI fragment of about 0.4 kbp in the pRL7 insert DNA (pRL7-0.4 kbp) was subcloned in M13mpl8 and partially sequenced using Sanger’s
dideoxynucleotide chain termination method. Dot matrix comparison of this sequence with rice rDNA sequences revealed low homology
with the 25 S rDNA sequence of rice, however, hybridisation did not indicate any homology. 相似文献
998.
999.
兴安落叶松结实规律与长短枝习性的关系 总被引:1,自引:0,他引:1
1987年5月,大兴安岭林区发生的特大森林火灾,实属世界罕见,火灾面积达1.0×10~6ha 多。大量的火烧迹地亟待更新、无论是人工更新还是人工促进天然更新,其中关键的问题之一是种子的来源,在大兴安岭地区,兴 相似文献
1000.
应用细胞内微电极技术记录到37个培养大鼠搏动心肌细胞充氮前后和复氧后的电活动参数。结果提示:充氮10min后,最大舒张电位(MDP),最大除极速度(V_(max)),动作电位振幅(APA)和动作电位时程(APD)等参数明显降低;自发节律增快,并出现多种形式的节律失常。83.8%细胞在充氮后30min内停搏,16.2%在50min左右停搏。复氧后,86.5%细胞在5min内复跳,13.5%未能复跳;12.5%复跳细胞在复跳10min内再次停搏。复跳细胞的各项电活动参数在30min内未能恢复到充氮前水平(p<0.05),且呈现不同程度的各类异常电活动。本结果对进一步研究心肌细胞缺氧和复氧损伤有一定意义。 相似文献