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31.
Identification of eight determinants in the hemagglutinin molecule of influenza virus A/PR/8/34 (H1N1) which are recognized by class II-restricted T cells from BALB/c mice.
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W Gerhard A M Haberman P A Scherle A H Taylor G Palladino A J Caton 《Journal of virology》1991,65(1):364-372
Eight nonoverlapping regions of the hemagglutinin (HA) molecule of influenza virus A/PR/8/34 (PR8), which serve as recognition sites for class II-restricted T cells (TH) from BALB/c mice, have been identified in the form of 10- to 15-amino-acid-long synthetic peptides. These TH determinants are located between residues 110 to 313 of the HA1 polypeptide. From a total of 36 HA-specific TH clones and limiting-dilution cultures of independent clonal origins, 33 (90%) responded to stimulation with one of these peptides. The residual three TH clones appeared to recognize a single additional determinant on the HA1 polypeptide which could not be isolated, however, in the form of a stimulatory peptide. None of the motifs that have been proposed to typify TH determinants were displayed by more than half of these recognition sites. Most unexpected was the finding that none of the TH determinants was located in the ectodomain of the HA2 polypeptide that makes up roughly one-third of the HA molecule. Possible reasons for the preferential recognition of HA1 as opposed to HA2 by TH are discussed. 相似文献
32.
Hartmut Köttig Gerhard Rottner Karl-Friedrich Beck Michael Schweizer Eckhart Schweizer 《Molecular & general genetics : MGG》1991,226(1-2):310-314
Summary The fatty acid synthetase (FAS) gene FAS1 of the alkane-utilizing yeast Yarrowia lipolytica was cloned and sequenced. The gene is represented by an intron-free reading frame of 6228 by encoding a protein of 2076 amino acids and 229980 Da molecular weight. This protein exhibits a 58% sequence similarity to the corresponding Saccharomyces cerevisiae FAS -subunit. The sequential order of the five FAS1-encoded enzyme domains, acetyl transferase, enoyl reductase, dehydratase and malonyl/palmityl-transferase, is co-linear in both organisms. This finding agrees with available evidence that the functional organization of FAS genes is similar in related organisms but differs considerably between unrelated species. In addition, previously reported conflicting data concerning the 3 end of S. cerevisiae FAS1 were re-examined by genomic and cDNA sequencing of the relevant portion of the gene. Thereby, the translational stop codon was shown to lie considerably downstream of both published termination sites. The S. cerevisiae FAS1 gene thus has a corrected length of 6153 by and encodes a protein of 2051 amino acids and 228667 Da molecular weight. 相似文献
33.
Immunological identification of yeast SCO1 protein as a component of the inner mitochondrial membrane 总被引:4,自引:0,他引:4
Summary The SCO1 gene of Saccharomyces cerevisiae encodes a 30 kDa protein which is specifically required for a post-translational step in the accumulation of subunits 1 and 2 of cytochrome c oxidase (COXI and COXII). Antibodies directed against a -Gal::SCO1 fusion protein detect SCO1 in the mitochondrial fraction of yeast cells. The SCO1 protein is an integral membrane protein as shown by its resistance to alkaline extraction and by its solubilization properties upon treatment with detergents. Based on the results obtained by isopycnic sucrose gradient centrifugation and by digitonin treatment of mitochondria, SCO1 is a component of the inner mitochondrial membrane. Membrane localization is mediated by a stretch of 17 hydrophobic amino acids in the amino-terminal region of the protein. A truncated SCO1 derivative lacking this segment, is no longer bound to the membrane and simultaneously loses its biological function. The observation that membrane localization of SCO1 is affected in mitochondria of a rho
0 strain, hints at the possible involvement of mitochondrially coded components in ensuring proper membrane insertion. 相似文献
34.
35.
The maturation of zygotes formed by the fusion of two gametes is the essential part of the diploid phase of the Chlamydomonas reinhardtii sexual life cycle and results in mature zygotes competent to germinate. To understand the molecular mechanisms underlying zygote maturation and the attainment of competence for germination we isolated genomic clones representing three different genes that are specifically expressed in Chlamydomonas reinhardtii zygotes. Accumulation of the RNAs started more than 24 h after mating, setting these genes apart from genes expressed in young zygotes [9]. Upon light-induced germination of zygotes, the mRNAs disappeared. The patterns of RNA accumulation and disappearance were gene-specific and suggested a function of these genes in maturation and/or in initial steps of germination. 相似文献
36.
Summary A 3D1H–15N–13C triple resonance experiment is presented that contains exclusively cross peaks between the1HN and15N nuclei of one residue with the H of the preceding residue. The pulse sequence, designed to minimize the time coherence, is transverse on nuclei with short T2 values. The experiment consists of coherence transfers via one-bond couplings from the HN via N, CO, C to the H and back to the HN for detection; it is called HN(COCA)HA. The experiment was tested on uniformly15N- and13C-enriched T4 lysozyme. 相似文献
37.
Microbial growth on carbon monoxide 总被引:14,自引:0,他引:14
The utilization of carbon monoxide as energy and/or carbon source by different physiological groups of bacteria is described and compared. Utilitarian CO oxidation which is coupled to the generation of energy for growth is achieved by aerobic and anaerobic eu- and archaebacteria. They belong to the physiological groups of aerobic carboxidotrophic, facultatively anaerobic phototrophic, and anaerobic acetogenic, methanogenic or sulfate-reducing bacteria. The key enzyme in CO oxidation is CO dehydrogenase which is a molybdo iron-sulfur flavoprotein in aerobic CO-oxidizing bacteria and a nickel-containing iron-sulfur protein in anaerobic ones. In carboxidotrophic and phototrophic bacteria, the CO-born CO2 is fixed by ribulose bisphosphate carboxylase in the reductive pentose phosphate cycle. In acetogenic, methanogenic, and probably in sulfate-reducing bacteria, CODH/acetyl-CoA synthase directly incorporates CO into acetyl-CoA.In plasmid-harbouring carboxidotrophic bacteria, CO dehydrogenase as well as enzymes involved in CO2 fixation or hydrogen utilization are plasmid-encoded. Structural genes encoding CO dehydrogenase were cloned from carboxidotrophic, acetogenic and methanogenic bacteria. Although they are clustered in each case, they are genetically distinct.Soil is a most important biological sink for CO in nature. While the physiological microbial groups capable of CO oxidation are well known, the type and nature of the microorganisms actually representing this sink are still enigmatic. We also tried to summarize the little information available on the nutritional and physicochemical requirements determining the sink strength. Because CO is highly toxic to respiring organisms even in low concentrations, the function of microbial activities in the global CO cycle is critical. 相似文献
38.
Günther Gätje Volker Müller Gerhard Gottschalk 《Applied microbiology and biotechnology》1991,34(6):778-782
Summary During growth on a complex medium containing 2% (w/v) lactose, Lactobacillus helveticus produced about 180 mm lactate. Due to the acidification, the external pH decreased to 3.7. The pH remained constant at a level of 0.5–0.7 units (40 mV), and µLac decreased gradually from –60 to 0 mV. The mechanism of lactate extrusion was studied with resting cells. Upon dilution of lactate-loaded cells in a buffer containing [14C]-lactate, a typical counterflow was observed, suggesting that a carrier system was employed in lactate excretion. Influx of lactate could not be driven by an artificial membrane potential, indicating that lactate was electroneutrally transported. By examining efflux under various lactate anion and lactic acid concentrations, the undissociated form of the acid was shown to influence the velocity of the transport process. A pH-dependent apparent K
m value of the carrier system was observed in efflux experiments with increasing internal lactate concentrations. It was concluded that the mode of end-product excretion can be defined as a carrier-mediated facilitated diffusion with the undissociated lactic acid or the lactate anion in symport with one proton, respectively, as the object of transport.Abbreviations
L
tota
total lactate
-
L
undissb
free lactic acid
-
L
dissc
lactate anion
- pHed
external pH
- pHie
internal pH
- pH
transmembrane H+ gradient
- µLacf
transmembrane gradient of total lactate
- µHLg
transmembrane gradient of the free lactic acid
- µLh
transmembrane gradient of the lactate anion
-
V
Effii
efflux velocity
Offprint requests to: G. Gottschalk 相似文献
39.
Stefan Schlatt Gerhard F. Weinbauer Eberhard Nieschlag 《Cell and tissue research》1991,265(2):203-209
Summary Inhibin-like immunoreactivity was detected by immunocytochemistry in the pituitaries of untreated male crab-eating macaques (cynomolgus monkey) and rhesus monkeys, in rhesus monkeys actively immunized against FSH, and in one orchidectomized crab-cating macaque. Localizations were performed by the immunogold-silver staining with 5-nm colloidal gold-conjugated second or third antibodies and by the alkaline phosphatase-anti-alkaline-phosphatase technique. Two different inhibin-specific antisera, raised against the -subunit or the entire inhibin molecule, provided identical staining patterns. Positive label was confined to the pars distalis of the pituitary and occurred exclusively in the cytoplasm of morphologically different cell types throughout the pars distalis in all pituitaries. Staining was most prominent in clusters of chromophobic cells. The presence of inhibin-like activity in the pituitary of an orchidectomized monkey with undetectable serum inhibin levels suggests that inhibin is produced within the pituitary gland. Co-localization studies for the -subunits of the gonadotropic hormones revealed that on average 82% of the gonadotropes were bihormonal. Using the same protocol, co-localization of inhibin-like activity with gonadotropin-like immunoreactivity revealed only a small degree of common distribution (<15%). Inhibinpositive cells were frequently in close proximity to gonadotropic cells and, thus, paracrine effects of inhibin on gonadotropin-synthesizing cells are conceivable. 相似文献
40.
Several quinolizidine alkaloids, including various angelate esters, are known from the genus Pearsonia. In a detailed variation study which included 98 samples from nine of the 11 species, large qualitative and quantitative differences were recorded. The observed variation is ascribed to the following: 1, species (the alkaloids of some species and subspecies are diagnostically different); 2, provenance (various populations of the same species may have unique combinations of alkaloids); 3, developmental stage (in P. cajanifolia there is a marked decreased in esterification towards the end of the growing season); 4, plant parts extracted (seeds, for example, have high concentrations of hydroxylated lupanine-type alkaloids and only small amounts of esters). These results highlight some of the problems associated with the use of alkaloids as taxonomic characters. 相似文献