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Serpins in prokaryotes 总被引:7,自引:0,他引:7
Irving JA Steenbakkers PJ Lesk AM Op den Camp HJ Pike RN Whisstock JC 《Molecular biology and evolution》2002,19(11):1881-1890
Members of the serpin (serine proteinase inhibitor) superfamily have been identified in higher multicellular eukaryotes (plants and animals) and viruses but not in bacteria, archaea, or fungi. Thus, the ancestral serpin and the origin of the serpin inhibitory mechanism remain obscure. In this study we characterize 12 serpin-like sequences in the genomes of prokaryotic organisms, extending this protein family to all major branches of life. Notably, these organisms live in dramatically different environments and some are evolutionarily distantly related. A sequence-based analysis suggests that all 12 serpins are inhibitory. Despite considerable sequence divergence between the proteins, in four of the 12 sequences the region of the serpin that determines proteinase specificity is highly conserved, indicating that these inhibitors are likely to share a common target. Inhibitory serpins are typically prone to polymerization upon heating; thus, the existence of serpins in the moderate thermophilic bacterium Thermobifida fusca, the thermophilic bacterium Thermoanaerobacter tengcongensis, and the hyperthermophilic archaeon Pyrobaculum aerophilum is of particular interest. Using molecular modeling, we predict the means by which heat stability in the latter protein may be achieved without compromising inhibitory activity. 相似文献
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Rather recently it has become clear that prokaryotes (Archaea and Bacteria) are able to glycosylate proteins. A literature
survey revealed the different types of glycoproteins. They include mainly surface layer (S-layer) proteins, flagellins, and
polysaccharide-degrading enzymes. Only in a few cases is structural information available. Many different structures have
been observed that display much more variation than that observed in eukaryotes. A few studies have given evidence for the
function of the prokaryotic glycoprotein glycans. Also from the biosynthetic point of view, information is rather scarce.
Due to their different cell structure, prokaryotes have to use mechanisms different from those found in eukaryotes to glycosylate
proteins. However, from the fragmented data available for the prokaryotic glycoproteins, similarities with the eukaryotic
system can be noticed.
Received: 24 February 1997 / Accepted: 13 May 1997 相似文献
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Most of the well-characterized prokaryotic genomes consist of double-stranded DNA organized as a single circular chromosome 0.6–10 Mb in length and one or more circular plasmid species of 2 kb-1.7 Mb. The past few years, however, have revealed some major variations in genome organization. In addition, a recent accumulation of data has shown that the location and orientation of the genes and repeated sequences (including prophages and transposons) on and among these elements is not always random. Some of the non-randomness is probably the result of unique historical events; in other cases it reflects selection for the optimization of function. 相似文献
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Circadian clocks in prokaryotes 总被引:7,自引:0,他引:7
Carl Hirschie Johnson Susan S. Golden Masahiro Ishiura & Takao Kondo 《Molecular microbiology》1996,21(1):5-11
Prokaryotes have long been thought incapable of expressing circadian (daily) rhythms. Recently, however, such biological 'clocks' have been discovered in several species of cyanobacteria. These endogenous timekeepers control gene expression on a global level in cyanobacteria. Even in cyanobacterial cultures that are growing with average doubling times more rapid than one per 24 h, the circadian clock controls gene expression and cell division. We have isolated mutants of the cyanobacterial circadian pacemaker and are currently characterizing the loci responsible for their altered period phenotypes. 相似文献
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Photoregulation of plant gene expression 总被引:5,自引:0,他引:5
R. John Ellis 《Bioscience reports》1986,6(2):127-136
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Magnetosome formation in prokaryotes 总被引:23,自引:0,他引:23
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T. P. Begley Diana M. Downs Steven E. Ealick Fred W. McLafferty Adolphus P. G. M. Van Loon Sean Taylor Nino Campobasso Hsiu-Ju Chiu Cynthia Kinsland Jason J. Reddick Jun Xi 《Archives of microbiology》1999,171(5):293-300
Twelve genes involved in thiamin biosynthesis in prokaryotes have been identified and overexpressed. Of these, six are required
for the thiazole biosynthesis (thiFSGH, thiI, and dxs), one is involved in the pyrimidine biosynthesis (thiC), one is required for the linking of the thiazole and the pyrimidine (thiE), and four are kinase genes (thiD, thiM, thiL, and pdxK). The specific reactions catalyzed by ThiEF, Dxs, ThiDM, ThiL, and PdxK have been reconstituted in vitro and ThiS thiocarboxylate
has been identified as the sulfur source. The X-ray structures of thiamin phosphate synthase and 5-hydroxyethyl-4-methylthiazole
kinase have been completed. The genes coding for the thiamin transport system (thiBPQ) have also been identified. Remaining problems include the cloning and characterization of thiK (thiamin kinase) and the gene(s) involved in the regulation of thiamin biosynthesis. The specific reactions catalyzed by
ThiC (pyrimidine formation), and ThiGH and ThiI (thiazole formation) have not yet been identified.
Received: 23 August 1998 / Accepted: 16 January 1999 相似文献
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Abstract We have reported previously on the presence of vertebrate-type peptide hormones in Tetrahymena pyriformis and Escherichia coli . We now have examined other prokaryotes for immunologically detectable insulin-like material. The bacteria studied were E. coli, Acinetobacter calcoaceticus RAG-1, Bordetella pertussis and Halobacteria solinarium; they were grown in defined minimal salt media under varying growth conditions. All these bacteria contain insulin-related material (1–12 pg per g cell wet wt). No insulin immunoactivity was detected in the media prior to inoculation. The content of insulin-related material was not affected by the carbon source used for cell growth. These data are in good agreement with data published previously, and suggest that prokaryotes and unicellular eukaryotes are capable of producing hormone-like material; the function of these peptides, if any, is as yet unknown. 相似文献
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Silent genes in prokaryotes 总被引:2,自引:0,他引:2
I.R. Beacham 《FEMS microbiology letters》1987,46(4):409-417
Abstract DNA sequence analysis provides excellent evidence for the origin of new genes, encoding new enzyme specificities or isozymes, via gene-duplication. New genes which arise in this way are likely to have arisen via silent gene intermediates. Such 'silent' genes are conceptually distinct from 'cryptic' genes which may also be silent; whereas cryptic genes are thought to be retained due to periodic selection, silent genes would be expected to have only a transient existence in the genome. Only very few of the known inactive genes are possibly (and with varying degrees of likelihood) of the 'silent' type. 相似文献
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Protein acetylation in prokaryotes 总被引:1,自引:0,他引:1
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Background
Oxygen is both essential and toxic to all forms of aerobic life and the chemical versatility and reactivity of thiols play a key role in both aspects. Cysteine thiol groups have key catalytic functions in enzymes but are readily damaged by reactive oxygen species (ROS). Low-molecular-weight thiols provide protective buffers against the hazards of ROS toxicity. Glutathione is the small protective thiol in nearly all eukaryotes but in prokaryotes the situation is far more complex.Scope of review
This review provides an introduction to the diversity of low-molecular-weight thiol protective systems in bacteria. The topics covered include the limitations of cysteine as a protector, the multiple origins and distribution of glutathione biosynthesis, mycothiol biosynthesis and function in Actinobacteria, recent discoveries involving bacillithiol found in Firmicutes, new insights on the biosynthesis and distribution of ergothioneine, and the potential protective roles played by coenzyme A and other thiols.Major conclusions
Bacteria have evolved a diverse collection of low-molecular-weight protective thiols to deal with oxygen toxicity and environmental challenges. Our understanding of how many of these thiols are produced and utilized is still at an early stage.General significance
Extensive diversity existed among prokaryotes prior to evolution of the cyanobacteria and the development of an oxidizing atmosphere. Bacteria that managed to adapt to life under oxygen evolved, or acquired, the ability to produce a variety of small thiols for protection against the hazards of aerobic metabolism. Many pathogenic prokaryotes depend upon novel thiol protection systems that may provide targets for new antibacterial agents. This article is part of a Special Issue entitled Cellular functions of glutathione. 相似文献15.
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Hiroko Yatsuhashi 《Journal of plant research》1996,109(2):139-146
Movements of the chloroplasts induced by a directional stimulus of light are found to occur in various plant materials ranging
from algae to terrestrial angiosperms. Depending on the fluence rate of light, chloroplasts move toward the area of the maximum
light absorption and escape from it, which are named as low- and high-fluence-rate responses, respectively. In most materials
the effective wavelengths are exclusively found in the blue-UV region of spectrum, (a) flavin pigment(s) being considered
as the photoreceptor, while in a few species of plants phytochrome is involved. The arrangement of chloroplasts as a result
of the movement depends on the orientation of the electrical vector of light, which reflects the dichroic orientation of the
photoreceptor for perception of light direction. Photosystems involved in these responses, however, are not only for perception
of light direction, but also for realization of the movement and for holding of the chloroplasts in the reached site. Possible
interactions and dual roles of photosystems in regulation of chloroplast movement are discussed. 相似文献
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