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Regularly arrayed surface (glyco)proteins—often referred to as S layers—are a common feature of the cell envelopes of almost all archaebacteria. We have selected some examples (Halobacterium, Sulfolobus, Thermoproteus, Pyrobaculum, Staphylothermus), and we describe the structure of their surface layers as revealed primarily by electron crystallography. In spite of a considerable diversity in shapes and dimensions, some common structural features emerge from the comparison. The glycoprotein arrays are composed of oligomeric units which are anchored in the plasma membrane; extended spacer or linker domains maintain the bulk of the more or less porous surface layers at a constant distance above the membrane surface, thus creating a quasi-periplasmic compartment. Functions ascribed to surface layers, such as compartmentalization, shape maintenance and determination, and adhesion are discussed. 相似文献
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Histidine supported good growth of Alcaligenes eutrophus strain H 16 as a nitrogen source, but only poor growth as a carbon and energy source. The facultative chemolithoautotrophic bacterium was also able to utilize urocanic acid, the first intermediate of histidine catabolism. The products of histidine degradation were ammonium, formate and glutamate. Three enzymes of the pathway, histidase, urocanase and formiminoglutamate hydrolase, were present in histidine-grown cells. Two types of spontaneous mutants, derived from the wild type, were characterized by an increased growth rate on histidine. One of these types was found to produce histidase constitutively and at a higher activity compared with the parental strain. The second type of mutant had apparently gained an improved histidine uptake system, which is supposed to be growth rate-limiting in the wild type. From the physiological studies the conclusion was drawn that the control of histidine-degrading enzymes is based on induction by urocanate and catabolite repression by carbon sources supporting fast growth, such as succinate or pyruvate. Ammonium was found not to affect catabolite repression, however, we obtained evidence that histidine uptake is subject to a nitrogen control.Abbreviation CTAB
hexadecyltrimethylammonium bromide 相似文献
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Summary Hagfish hemoglobin has three main components, one of which is Hb III. It is monomeric and consists of 148 amino acid residues (M = 17 350). Its complete primary structure, previously published, is discussed here. The proximal amino acid (F8) of the heme linkage is histidine as always in the hemoglobins, but the regularly expected distal histidine E7 is substituted by glutamine. This substitution, leading to a new kind of heme linkage, has hitherto only been demonstrated in opossum hemoglobin. It is suggested that E7, Gln, is directed out of the heme pocket, and that the adjacent Ell, Ile, is directed toward the inside of the pocket, giving the distal heme contact instead of histidine.Myxine Hb III has an additional tail of 9 amino acid residues at its N-terminal end, as has the hemoglobin ofLampetra fluviatilis. The genetic codes ofMyxine andLampetra hemoglobins show 117 differences, in spite of many morphological resemblances between hagfish and lamprey. Their primary hemoglobin structures show differences substantial enough to bo compatible with the divergence of the two families some 400–500 million years ago. 相似文献
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Uli Ohmayer Michael Gamalinda Martina Sauert Julius Ossowski Gisela P?ll Jan Linnemann Thomas Hierlmeier Jorge Perez-Fernandez Beril Kumcuoglu Isabelle Leger-Silvestre Marlène Faubladier Joachim Griesenbeck John Woolford Herbert Tschochner Philipp Milkereit 《PloS one》2013,8(7)
During the assembly process of ribosomal subunits, their structural components, the ribosomal RNAs (rRNAs) and the ribosomal proteins (r-proteins) have to join together in a highly dynamic and defined manner to enable the efficient formation of functional ribosomes. In this work, the assembly of large ribosomal subunit (LSU) r-proteins from the eukaryote S. cerevisiae was systematically investigated. Groups of LSU r-proteins with specific assembly characteristics were detected by comparing the protein composition of affinity purified early, middle, late or mature LSU (precursor) particles by semi-quantitative mass spectrometry. The impact of yeast LSU r-proteins rpL25, rpL2, rpL43, and rpL21 on the composition of intermediate to late nuclear LSU precursors was analyzed in more detail. Effects of these proteins on the assembly states of other r-proteins and on the transient LSU precursor association of several ribosome biogenesis factors, including Nog2, Rsa4 and Nop53, are discussed. 相似文献
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Jazmin M. Pérez-Rojas Cristino Cruz Patricia García-López Dolores J. Sánchez-González Claudia M. Martínez-Martínez Gisela Ceballos 《Free radical research》2013,47(11):1122-1132
Cisplatin (CDDP) is a chemotherapeutic agent that produces nephrotoxicity associated with oxidative/nitrosative stress. α-Mangostin (α-M) is a xanthone extracted from mangosteen with antioxidant and anti-inflammatory properties. The purpose of this study was to evaluate the renoprotective effect of α-M on the CDDP-induced nephrotoxicity. α-M was administered (12.5 mg/kg/day, i.g.) for 10 days (7 days before and 3 days after CDDP injection). On day 7, rats were treated with a single injection of CDDP (7.5 mg/Kg, i.p.); 3 days after the rats were killed. α-M attenuated renal dysfunction, structural damage, oxidative/nitrosative stress, decrease in catalase expression and increase in mRNA levels of tumour necrosis factor alpha and transforming growth factor beta. In conclusion the renoprotective effect of α-M on CDDP-induced nephrotoxicity was associated with the attenuation in oxidative/nitrosative stress and inflammatory and fibrotic markers and preservation of catalase activity. 相似文献
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Three types of epidermal cultures of fish were used for toxicological investigations, a primary cell culture and a tissue culture prepared from the rainbow trout Oncorhynchus mykiss Walbaum and the cell line EPC, derived from a skin tumour of the carp Cyprinus carpio L. Two studies were carried out to compare the different culture systems. In the first cultures were incubated with nonylphenol and in the second set of experiments the cell cultures were exposed to a wastewater sample containing low concentrations of nonylphenol (NP). Both cell cultures were similarly sensitive to nonylphenol with respect to the endpoints cell viability (LC50 (24 h) 47.1 μM NP (primary cell culture) and 44.2 μM NP (EPC)) values and apoptotic rate (significantly increased apoptotic rate after exposure to 50 μM NP for 24 h, p < 0.001 (primary cell culture), p = 0.008 (EPC)). The explant culture was slightly less sensitive (increased apoptotic rate after exposure to 50 μM NP for 24 h, but not significant: p = 0.385), which could be due to the capabilities of a differentiated tissue, providing more protective repair mechanisms, compared with single cells. All cultures revealed a concentration–response relationship for the endpoint apoptotic rate after the application of nonylphenol for 24 h. After wastewater exposure, a significant decrease in the apoptotic rate was measured in the primary cell culture (dilution wastewater : medium 1:1:p = 0.018; dilution wastewater : medium 1:2:p = 0.003), whereas the cell line EPC did not reveal any effects. Our results show that the endpoint apoptotic rate is more sensitive than the parameter cell viability for detecting adverse effects of a wastewater sample. 相似文献