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31.
Elfriede Stellbogen 《Zoomorphology》1930,19(4):686-731
Ohne Zusammenfassung 相似文献
32.
Pietsch D Bernát G Kahmann U Staiger D Pistorius EK Michel KP 《Photosynthesis research》2011,108(2-3):121-132
Iron limitation has a strong impact on electron transport reactions of the unicellular fresh water cyanobacterium Synechococcus elongatus PCC 7942 (thereafter referred to as S.?elongatus). Among the various adaptational processes on different cellular levels, iron limitation induces a strongly enhanced expression of IdiC (iron-deficiency-induced protein C). In this article, we show that IdiC is loosely attached to the thylakoid and to the cytoplasmic membranes and that its expression is enhanced during conditions of iron starvation and during the late growth phase. The intracellular IdiC level was even more increased when additional iron was replenished in the late growth phase. On the basis of its amino acid sequence and of its absorbance spectrum, IdiC can be classified as a member of the family of thioredoxin (TRX)-like (2Fe-2S) ferredoxins. The presence of an iron cofactor in IdiC was detected by inductive coupled plasma optical emission spectrometry (ICP-OES). Comparative measurements of electron transport activities of S.?elongatus wild type (WT) and an IdiC-merodiploid mutant called MuD, which contained a strongly reduced IdiC content under iron-sufficient as well as iron-deficient growth conditions, were performed. The results revealed that MuD had a strongly increased light sensitivity, especially under iron limitation. The measurements of photosystem II (PS II)-mediated electron transport rates in WT and MuD strain showed that PS II activity was significantly lower in MuD than in the WT strain. Moreover, P(700) (+) re-reduction rates provided evidence that the respiratory activities, which were very low in the MuD strain in the presence of iron, significantly increased in iron-starved cells. Thus, an increase in respiration may compensate for the drastic decrease of photosynthetic electron transport activity in MuD grown under iron starvation. Based on the similarity of the S. elongatus IdiC to the NuoE subunit of the NDH-1 complex in Escherichia coli, it is likely that IdiC has a function in the electron transport processes from NAD(P)H to the plastoquinone pool. This is in agreement with the up-regulation of IdiC in the late growth phase as well as under stress conditions when PS II is damaged. As absence or high reduction of the IdiC level would prevent or reduce the formation of functional NDH-1 complexes, under such conditions electron transport routes via alternative substrate dehydrogenases, donating electrons to the plastoquinone pool, can be assumed to be up-regulated. 相似文献
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Gau AE Heindl A Nodop A Kahmann U Pistorius EK 《Zeitschrift für Naturforschung. C, Journal of biosciences》2007,62(3-4):273-284
The two closely related fresh water cyanobacteria Synechococcus elongatus PCC 6301 and Synechococcus elongatus PCC 7942 have previously been shown to constitutively express a FAD-containing L-amino acid oxidase with high specificity for basic L-amino acids (L-arginine being the best substrate). In this paper we show that such an enzyme is also present in the fresh water cyanobacterium Synechococcus cedrorum PCC 6908. In addition, an improved evaluation of the nucleotide/amino acid sequence of the L-amino acid oxidase of Synechococcus elongatus PCC 6301 (encoded by the aoxA gene) with respect to the FAD-binding site and a translocation pathway signal sequence will be given. Moreover, the genome sequences of 24 cyanobacteria will be evaluated for the occurrence of an aoxA-similar gene. In the evaluated cyanobacteria 15 genes encoding an L-amino acid oxidase-similar protein will be found. 相似文献
35.
Bendz H Ruhland SC Pandya MJ Hainzl O Riegelsberger S Braüchle C Mayer MP Buchner J Issels RD Noessner E 《The Journal of biological chemistry》2007,282(43):31688-31702
Heat shock proteins (HSPs) have shown promise for the optimization of protein-based vaccines because they can transfer exogenous antigens to dendritic cells and at the same time induce their maturation. Great care must be exercised in interpretating HSP-driven studies, as by-products linked to the recombinant generation of these proteins have been shown to mediate immunological effects. We generated highly purified human recombinant Hsp70 and demonstrated that it strongly enhances the cross-presentation of exogenous antigens resulting in better antigen-specific T cell stimulation. Augmentation of T cell stimulation was a direct function of the degree of complex formation between Hsp70 and peptides and correlated with improved antigen delivery to endosomal compartments. The Hsp70 activity was independent of TAP proteins and was not inhibited by exotoxin A or endosomal acidification. Consequently, Hsp70 enhanced cross-presentation of various antigenic sequences, even when they required different post-uptake processing and trafficking, as exemplified by the tumor antigens tyrosinase and Melan-A/MART-1. Furthermore, Hsp70 enhanced cross-presentation by different antigen-presenting cells (APCs), including dendritic cells and B cells. Importantly, enhanced cross-presentation and antigen-specific T cell activation were observed in the absence of innate signals transmitted by Hsp70. As Hsp70 supports the cross-presentation of different antigens and APCs and is inert to APC function, it may show efficacy in various settings of immune modulation, including induction of antigen-specific immunity or tolerance. 相似文献
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Cordeiro LM Reis RA Cruz LM Stocker-Wörgötter E MartinGrube Iacomini M 《FEMS microbiology ecology》2005,54(3):381-390
A light microscopic and molecular analysis of photobionts in Ramalina and Cladonia from coastal habitats of Brazil is presented. A Bayesian phylogenetic analysis of ITS rDNA sequences suggests a Trebouxia lineage which is preferentially tropical in geographic distribution. This highly diverse clade also includes the morphological similar species Trebouxia higginsiae and galapagensis. Within the predominantly tropical clade of Trebouxia we distinguish several subclades, three of which are represented in our samples of Ramalina species. Since sexuality has not been recognized in coccal lichenised photobionts until recently, we cannot apply a biological species concept, but when compared with the sequence diversity between known species we conclude that several new species need to be described in this clade. The mutually exclusive presence of other Trebouxia lineages in temperate samples of Ramalina suggests an evolution towards higher selectivity in this genus. A strictly tropical lineage is not conspicuous in the photobionts of the genus Asterochloris sampled from Cladonia so far. 相似文献
40.
Production of cyanophycin, a suitable source for the biodegradable polymer polyaspartate, in transgenic plants 总被引:3,自引:0,他引:3
Neumann K Stephan DP Ziegler K Hühns M Broer I Lockau W Pistorius EK 《Plant biotechnology journal》2005,3(2):249-258
The production of biodegradable polymers in transgenic plants in order to replace petrochemical compounds is an important challenge for plant biotechnology. Polyaspartate, a biodegradable substitute for polycarboxylates, is the backbone of the cyanobacterial storage material cyanophycin. Cyanophycin, a copolymer of l-aspartic acid and l-arginine, is produced via non-ribosomal polypeptide biosynthesis by the enzyme cyanophycin synthetase. A gene from Thermosynechococcus elongatus BP-1 encoding cyanophycin synthetase has been expressed constitutively in tobacco and potato. The presence of the transgene-encoded messenger RNA (mRNA) correlated with changes in leaf morphology and decelerated growth. Such transgenic plants were found to produce up to 1.1% dry weight of a polymer with cyanophycin-like properties. Aggregated material, able to bind a specific cyanophycin antibody, was detected in the cytoplasm and the nucleus of the transgenic plants. 相似文献