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91.
D. L. Jennings 《Genetica》1964,35(1):152-164
Lethal or chronic diseases of the raspberry caused by the nematodeborne viruses raspberry ringspot, arabis mosaic and tomato black ring can cause serious reductions in the productivity of raspberry plantations, but the existence of clear-cut immunities from these diseases provides a basis for control through plant breeding. The inheritance of these immunities was studied by means of graft tests on families of raspberry seedlings. Immunity from each virus was found to be dominant to susceptibility, but there was evidence that more than one gene was concerned in each case: while it was not possible to decide whether the second gene was a dominant complementary or a linked recessive affecting the viability of the immune segregates, the frequent occurrence in the raspberry of aberrant segregation ratios due to such lethal genes makes the latter explanation the more probable. There was also evidence of linkage between the genes for the three immunities. The experiment confirmed the practicability of breeding to incorporate genes for immunities from these three viruses into new raspberry varieties. 相似文献
92.
Opc- and pilus-dependent interactions of meningococci with human endothelial cells: molecular mechanisms and modulation by surface polysaccharides 总被引:23,自引:4,他引:23
Mumtaz Virji Katherine Makepeace Ian R.A. Peak David J.P. Ferguson Michael P. Jennings E. Richard Moxon 《Molecular microbiology》1995,18(4):741-754
The interplay between four surface-expressed virulence factors of Neisseria meningitidis (pili, Opc, capsule and lipopolysaccharide (LPS)) in host cell adhesion and invasion was examined using derivatives of a serogroup B strain, MC58, created by mutation (capsule, Opc) and selection of variants. To examine the role of Opc and of additional expression of pili, bacteria lacking the expression of Opa proteins were used. The effects of different LPS structures were examined in variants expressing either sialylated (L3 immunotype) or truncated non-sialylated (L8 immuno-type) LPS. Studies showed that (i) pili were essential for meningococcal interactions with host cells in both capsulate and acapsulate bacteria with the sialylated L3 LPS immunotype, (ii) the Opc-mediated invasion of host cells by piliated and non-piliated bacteria was observed only in acapsulate organisms with L8 LPS immunotype, and (iii) expression of pili in Opc-expressing bacteria resulted in increased invasion. Investigations on the mechanisms of cellular invasion indicated that the Opc-mediated invasion was dependent on the presence of serum in the incubation medium and was mediated by serum proteins with arginine-glycine-aspartic acid (RGD) sequence. Cellular invasion in piliated Opc+ phenotype also required bridging molecules containing the RGD recognition sequence and appeared to involve the integrin αvβ3 as a target receptor on endothelial cells. These studies extend the previous observations on variants of a serogroup A strain (C751) and show that Opc mediates cellular invasion in distinct meningococcal strains and provide confirmation of its mechanism of action. This is the first investigation that evaluates, using derivatives of a single strain, the interplay between four meningococcal surface virulence factors in host cell invasion. 相似文献
93.
TRIAD3/RNF216 mutations associated with Gordon Holmes syndrome lead to synaptic and cognitive impairments via Arc misregulation 下载免费PDF全文
Nilofer Husain Qiang Yuan Yi‐Chun Yen Olga Pletnikova Dong Qianying Sally Paul Worley Zoë Bichler H. Shawn Je 《Aging cell》2017,16(2):281-292
Multiple loss‐of‐function mutations in TRIAD3 (a.k.a. RNF216) have recently been identified in patients suffering from Gordon Holmes syndrome (GHS), characterized by cognitive decline, dementia, and movement disorders. TRIAD3A is an E3 ubiquitin ligase that recognizes and facilitates the ubiquitination of its target for degradation by the ubiquitin‐proteasome system (UPS). Here, we demonstrate that two of these missense substitutions in TRIAD3 (R660C and R694C) could not regulate the degradation of their neuronal target, activity‐regulated cytoskeletal‐associated protein (Arc/Arg 3.1), whose expression is critical for synaptic plasticity and memory. The synaptic deficits due to the loss of endogenous TRIAD3A could not be rescued by TRIAD3A harboring GHS‐associated missense mutations. Moreover, we demonstrate that the loss of endogenous TRIAD3A in the mouse hippocampal CA1 region led to deficits in spatial learning and memory. Finally, we show that these missense mutations abolished the interaction of TRIAD3A with Arc, disrupting Arc ubiquitination, and consequently Arc degradation. Our current findings of Arc misregulation by TRIAD3A variants suggest that loss‐of‐function mutations in TRIAD3A may contribute to dementia observed in patients with GHS driven by dysfunctional UPS components, leading to cognitive impairments through the synaptic protein Arc. 相似文献
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The equilibrium structural ensemble of a 20-residue polyglutamic acid peptide (E(20)) was studied with FRET, circular dichroism, and molecular dynamics (MD) simulations. A FRET donor, o-aminobenzamide, and acceptor, 3-nitrotyrosine, were introduced at the N- and C-termini, respectively. Circular dichroism, steady state FRET, and time-resolved FRET measurements were employed to characterize the fraction helix and end-to-end distance under different pH conditions: pH 4 (60% alpha-helix), pH 6 (0% alpha-helix), and pH 9 (0% alpha-helix). At pH 4, the end-to-end distance was measured at 24 A and determined to be considerably less than the 31 A predicted for an alpha-helix of the same length. At pH 6 and 9, the end-to-end distance was measured at > 31 and 39 A respectively, both which are determined to be considerably greater than the 27 A predicted for a freely jointed random coil of the same length. To better understand the physical forces underlying the unusual helix-coil transition in this peptide, three theoretical MD models of E(20) were constructed: (1) a pure alpha-helix, (2) an alpha-helix with equivalent attractive intramolecular contacts, and (3) a weak alpha-helix with termini-weighted intramolecular contacts ("sticky ends"). Using MD simulations, the bent helix structure calculated from Model 3 was found to be the closest in agreement with the experimental data. 相似文献
98.
Recently it has been observed that multicopper oxidases are present in a number of microbial genomes, raising the question of their function in prokaryotes. Here we describe the analysis of an mco mutant from the opportunistic pathogen Pseudomonas aeruginosa. Unlike wild-type Pseudomonas aeruginosa, the mco mutant was unable to grow aerobically on minimal media with Fe(II) as sole iron source. In contrast, both the wild-type and mutant strain were able to grow either anaerobically via denitrification with Fe(II) or aerobically with Fe(III). Analysis of iron uptake showed that the mco mutant was impaired in Fe(II) uptake but unaffected in Fe(III) uptake. Purification and analysis of the MCO protein confirmed ferroxidase activity. Taken together, these data show that the mco gene encodes a multicopper oxidase that is involved in the oxidation of Fe(II) to Fe(III) subsequent to its acquisition by the cell. In view of the widespread distribution of the mco gene in bacteria, it is suggested that an iron acquisition mechanism involving multicopper oxidases may be an important and hitherto unrecognized feature of bacterial pathogenicity. 相似文献
99.
This study is concerned with the development of kinetic-based bioaffinity chromatographic systems for purification of ATP-dependent kinases, with a particular focus on the allosteric yeast hexokinase enzyme (EC 2.7.1.1). Synthesis and characterization of highly substituted N(6)-linked and S(6)-linked immobilized ATP derivatives are described using a rapid solid-phase modular approach. Evaluation of the new immobilized ATP derivatives has been carried out using model chromatographic studies with yeast hexokinase, employing specific substrate analogues (N-acetyl-D-glucosamine and suramin) to promote biospecific adsorption, in the presence and absence of citrate (a so-called allosteric activator of hexokinase activity). In this paper, successful bioaffinity chromatography systems were developed for yeast hexokinase and, as a result, interesting binding and catalytic properties of the enzyme were highlighted and explored. The overall results confirm the potential for extrapolation of the kinetic locking-on tactic, a general kinetic-based bioaffinity approach already developed for the NAD(P)(+)-dependent dehydrogenases, to ATP/ADP-dependent enzymes. However, in view of the enhancement of the intrinsic ATPase activity of hexokinase with glucosamine derivatives, and the coincidental hydrolysis of immobilized ATP to immobilized ADP, future developments necessary to support adaptation of the approach to ATP-dependent enzymes are discussed. 相似文献
100.
Michael P. Jennings Peter van der Ley Kathy E. Wilks Duncan J. Maskell † Jan T. Poolman E. Richard Moxon 《Molecular microbiology》1993,10(2):361-369
The galE gene from Haemophilus influenzae was used as a hybridization probe for the galE gene of Neisseria meningitidis Group B, identifying two different homologous loci. Each of the loci was cloned and nucleotide sequence analysis revealed that both loci contained sequences similar to galE. One contained a functional galE gene and mapped to the capsule biosynthetic locus. The second contained only a partial galE-coding sequence, which did not express a functional gene product. A galE mutant meningococcal strain was constructed by transformation with an inactivated galE gene. Analysis of the LPS from the galE mutant strain revealed an apparent reduction in molecular weight and a loss of reactivity with monoclonal antibodies specific for structures known to contain galactose. These results are consistent with an essential role for galE in the incorporation of galactose into meningococcal lipopolysaccharide. 相似文献