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181.
182.
183.
The functional units of a peptostreptococcal protein L 总被引:4,自引:0,他引:4
Jonathan P. Murphy Clive J. Duggleby Max A. Atkinson † Angus R. Trowern Tony Atkinson Christopher R. Goward 《Molecular microbiology》1994,12(6):911-920
Protein L is a cell-surface protein from Peptostreptococcus which interacts with immunoglobulin kappa light chains. A gene from Peptostreptococcus strain 3316 coding for protein L and fragments thereof were expressed in Escherichia coli. The peptides were examined for binding to immunoglobulin and serum albumin. The four C units were shown to be responsible for binding to immunoglobulin and the four D units for binding to albumin. This protein L molecule therefore binds to albumin at a site separate from that involved in binding to immunoglobulin. The albumin-binding units have high amino acid sequence identity with the albumin-binding units of streptococcal cell-surface proteins. The gene contains three sites available for internal initiation of translation resulting in three active proteins. The protein L molecule presented in this report was compared with a previously reported protein from Peptostreptococcus strain 312. The two proteins differ in several respects, including size and the number and types of repeat units. 相似文献
184.
Simon Lovestone C. Hugh Reynolds Donna Latimer Daniel R. Davis Brian H. Anderton Jean-Marc Gallo Diane Hanger Sandrine Mulot Betina Marquardt Silvia Stabel James R. Woodgett Christopher C. J. Miller 《Current biology : CB》1994,4(12)
Background: Paired helical filaments (PHFs) are a characteristic pathological feature of Alzheimer's disease; their principal component is the microtubule-associated protein tau. The tau in PHFs (PHF-tau) is hyperphosphorylated, but the cellular mechanisms responsible for this hyperphosphorylation have yet to be elucidated. A number of kinases, including mitogen-activated protein (MAP) kinase, glycogen synthase kinase (GSK)-3α, GSK-3β and cyclin-dependent kinase-5, phosphorylate recombinant tau in vitro so that it resembles PHF-tau as judged by its reactivity with a panel of antibodies capable of discriminating between normal tau and PHF-tau, and by a reduced electrophoretic mobility that is characteristic of PHF-tau. To determine whether MAP kinase, GSK-3α and GSK-3β can also induce Alzheimer's disease-like phosphorylation of tau in mammalian cells, we studied the phosphorylation status of tau in primary neuronal cultures and transfected COS cells following changes in the activities of MAP kinase and GSK-3.Results Activating MAP kinase in cultures of primary neurons or transfected COS cells expressing tau isoforms did not increase the level of phosphorylation for any PHF-tau epitope investigated. But elevating GSK-3 activity in the COS cells by co-transfection with GSK-3α or GSK-3β decreased the electrophoretic mobility of tau so that it resembled that of PHF-tau, and induced reactivity with eight PHF-tau-selective monoclonal antibodies.Conclusion Our data indicate that GSK-3α and/or GSK-3β, but not MAP kinase, are good candidates for generating PHF-type phosphorylation of tau in Alzheimer's disease. The involvement of other kinases in the generation of PHFs cannot, however, be eliminated. Our results suggest that aberrant regulation of GSK-3 may be a pathogenic mechanism in Alzheimer's disease. 相似文献
185.
Christopher M. de Fiebre Ping Wu Dean Notabartolo William J. Millard Edwin M. Meyer 《Neurochemical research》1994,19(6):643-648
The ability of Sendai virosomes or LipofectinTM to introduce an AAV vector into primary rat brain astroglial cultures was characterized. The pJDT95npy vector was constructed by inserting rat NPY cDNA downstream from the indigenous AAV p5, p19 and p40 promoters in pJDT95. LipofectinTM-mediated transfection with pJDT95npy (10 g) resulted in pronounced expression of several NPY mRNA species: p5-driven (3.3 kb), p19-driven (2.7 kb) and p40-driven (0.6, 0.8, 1.1, and 1.8 kb). Exposure to virosomally encapsulated pJDT95npy (50 or 100 ng) resulted in transient expression of some p40-driven mRNA species (0.8 and 1.8 kb). Neither method produced astroglia cells which synthesized mature NPY immunoreactivity. This demonstrates that an AAV-derived vector can drive gene expression in astroglia, that Sendai virosomes can infuse vectors into astroglia, but that the amount of DNA infused in this manner may limit long term expression. 相似文献
186.
Glutamate receptors mediate the majority of excitatory neurotransmission in the brain, and molecular cloning studies have revealed several distinct families. Because neuropathological states and possibly human disorders may involve kainate-preferring glutamate receptors, we have isolated a cDNA clone for the human GluR6 kainate-preferring receptor. This clone shows a very high sequence similarity with that of the rat, except for a part of the 3′ untranslated region in which there is a TAA triplet repeat. When the protein was overexpressed in human embryonic kidney 293 cells, it had a molecular weight, an antibody recognition, and a glutamate ligand-binding profile similar to those of the rat GluR6 receptor. Northern analysis showed expression in both human cerebral and cerebellar cortices. By PCR analysis of rodent-human monochromosomal cell lines, the human GluR6 could be assigned to chromosome 6. The length of the TAA triplet repeat was polymorphic in the normal population, with at least four alleles and an observed heterozygosity of about 45%. These studies should provide the basis for expression or linkage studies of the GluR6 kainate receptor in human disease or neuropathologic states. 相似文献
187.
Similarly to higher plant root systems, Chlamydomonas reinhardtii Dangeard (UTEX 90) cells exhibited biphasic NO3? uptake kinetics. The uptake pattern was similar in cells cultured in 10 mM NO3? (NO3?-grown), 0.25 mM NO3? (N-limited) or 10 mM NO3? followed by an 18-h period of N-deprivation (N-starved). In all cell types there was an apparent phase transition in uptake at 1.1 mM NO3?, although there were variations in the uptake Vmax of both isotherms. The rate of uptake via isotherm 0 ([NO3?]<1.1 mM) in N-limited cells was higher than that of either NO3?-grown or N-starved cells. In contrast, NO3?-grown and N-limited cells exhibited comparable Vmax values when supplied with 1.1 to 1.8 mM NO3? (isotherm 1). When supplied with 1.6 mM NO3?, both N-limited and N-starved cells exhibited enhanced linear uptake after 60 min of incubation. We ascribed this to an induction phenomenon. This trend was not observed when NO3?-grown cells were supplied with 1.6 mM NO3?, or when N-limited and N-starved cells were supplied with 0.6 mM NO3?. The ‘inducible’ aspect of uptake by N-limited cells was blocked by cycloheximide (10 mg l?1), but not by actinomycin D (5 mg l?1), thus indicating the involvement of a translational or post-translational event. To investigate this phenomenon further, we analysed the cell proteins of N-limited cells supplied with either 0.6 or 1.6 mM NO3? for 90 min, using two-dimensional gel electrophoresis. Comparison of protein profiles enabled the identification of a single cell membrane-associated polypeptide (21 kDa, pI ca 5.5) and ten soluble fraction polypeptides (17–73 kDa, pI ca 5.0 to 7.1) unique to the high NO3? treatment. We propose that the ‘inducible’ portion of NO3? uptake may provide the means by which C. reinhardtii cells regulate uptake in accordance with assimilatory capacity. 相似文献
188.
Andrew N. Lane Christopher J. Bauer Thomas A. Frenkiel Andrew J. Birchall 《European biophysics journal : EBJ》1993,22(2):135-143
The majority of the 1H NMR resonances of the protons in a tetradecamer containing the —35 region of the trp promoter d(GCTGTTGACAATTA): d(TAATTGTCAACAGC) and in the TA transversion have been assigned. The conformational properties of the nucleotides have been determined and compared in the two duplexes. Analysis of spin-spin coupling and NOES shows that all sugar puckers are in the south domain (i.e. near C2 endo) and the glycosidic torsion angles are anti (110°). The NMR data are consistent with the duplex being in the B family of conformations. Significant differences in chemical shifts between the two molecules were observed only for nearest neighbours to the transversion site, suggesting the absence of long range conformational effects. This was confirmed by the similarity of coupling constants and NOEs. Other properties are also not greatly affected at positions more than two base pairs from the mutation site. These results are consistent with the hypothesis that unconstrained oligonucleotides are highly flexible, and can readily accommodate significant perturbations of the local structure, such as a transversion. 相似文献
189.
Phillip E. Klebba Jeanette M. Rutz Jun Liu Christopher K. Murphy 《Journal of bioenergetics and biomembranes》1993,25(6):603-611
The recent solution of enteric bacterial porin structure, and new insights into the mechanism by which outer membrane receptor proteins recognize and internalize specific ligands, advocates the re-evaluation of TonB-dependent transport physiology. In this minireview we discuss the potential structural features of siderophore receptors and TonB, and use this analysis to evaluate both existing and new models of energy and signal transduction from the inner membrane to the outer membrane of gram-negative bacteria. 相似文献
190.
Christopher M. R. Bax Vijai S. Shankar A. S. M. Towhidul Alam Bridget E. Bax Baljit S. Moonga Christopher L. -H. Huang Mone Zaidi Barry R. Rifkin 《Bioscience reports》1993,13(3):169-174
We report the effects of tetracycline analogues on cytosolic Ca2+ transients resulting from application of ionic nickel (Ni2+), a potent surrogate agonist of the osteoclast Ca2+ receptor. Preincubation with minocycline (1 mg/l) or a chemically modified tetracycline, 4-dedimethyl-aminotetracycline (CMT-1) (1 or 10 mg/l), resulted in a significant attenuation of the magnitude of the cytosolic [Ca2+] response to an application of 5 mM-[Ni2+]. Preincubation with doxycycline (1 or 10 mg/l) failed to produce similar results. In addition, application of minocycline alone (0.1–100 mg/l) resulted in a 3.5-fold elevation of cytosolic [Ca2+]. The results suggest a novel action of tetracyclines on the osteoclast Ca2+ receptor. 相似文献