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排序方式: 共有197条查询结果,搜索用时 15 毫秒
131.
132.
Pandinus imperator scorpion venom blocks voltage-gated potassium channels in GH3 cells 总被引:1,自引:1,他引:0
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We examined the effects of Pandinus imperator scorpion venom on voltage-gated potassium channels in cultured clonal rat anterior pituitary cells (GH3 cells) using the gigohm-seal voltage-clamp method in the whole-cell configuration. We found that Pandinus venom blocks the voltage-gated potassium channels of GH3 cells in a voltage-dependent and dose-dependent manner. Crude venom in concentrations of 50-500 micrograms/ml produced 50-70% block of potassium currents measured at -20 mV, compared with 25-60% block measured at +50 mV. The venom both decreased the peak potassium current and shifted the voltage dependence of potassium current activation to more positive potentials. Pandinus venom affected potassium channel kinetics by slowing channel opening, speeding deactivation slightly, and increasing inactivation rates. Potassium currents in cells exposed to Pandinus venom did not recover control amplitudes or kinetics even after 20-40 min of washing with venom-free solution. The concentration dependence of crude venom block indicates that the toxins it contains are effective in the nanomolar range of concentrations. The effects of Pandinus venom were mimicked by zinc at concentrations less than or equal to 0.2 mM. Block of potassium current by zinc was voltage dependent and resembled Pandinus venom block, except that block by zinc was rapidly reversible. Since zinc is found in crude Pandinus venom, it could be important in the interaction of the venom with the potassium channel. We conclude that Pandinus venom contains toxins that bind tightly to voltage-dependent potassium channels in GH3 cells. Because of its high affinity for voltage-gated potassium channels and its irreversibility, Pandinus venom may be useful in the isolation, mapping, and characterization of voltage-gated potassium channels. 相似文献
133.
Howe GT; Bucciaglia PA; Hackett WP; Furnier GR; Cordonnier-Pratt MM; Gardner G 《Molecular biology and evolution》1998,15(2):160-175
The phytochrome photoreceptors play important roles in the photoperiodic
control of vegetative bud set, growth cessation, dormancy induction, and
cold-hardiness in trees. Interestingly, ecotypic differences in
photoperiodic responses are observed in many temperate- zone tree species.
Northern and southern ecotypes of black cottonwood (Populus trichocarpa
Torr. & Gray), for example, exhibit marked differences in the timing of
short-day-induced bud set and growth cessation, and these responses are
controlled by phytochrome. Therefore, as a first step toward determining
the molecular genetic basis of photoperiodic ecotypes in trees, we
characterized the phytochrome gene (PHY) family in black cottonwood. We
recovered fragments of one PHYA and two PHYB using PCR-based cloning and by
screening a genomic library. Results from Southern analyses confirmed that
black cottonwood has one PHYA locus and two PHYB loci, which we arbitrarily
designated PHYB1 and PHYB2. Phylogenetic analyses which included PHY from
black cottonwood, Arabidopsis thaliana and tomato (Solanum lycopersicum)
suggest that the PHYB/D duplications in these species occurred
independently. When Southern blots were probed with PHYC, PHYE, and PHYE
heterologous probes, the strongest bands that we detected were those of
black cottonwood PHYA and/or PHYB. These results suggest that black
cottonwood lacks members of the PHYC/F and PHYE subfamilies. Although black
cottonwood could contain additional PHY that are distantly related to known
angiosperm PHY, our results imply that the PHY family of black cottonwood
is less complex than that of other well-characterized dicot species such as
Arabidopsis and tomato. Based on Southern analyses of five black cottonwood
genotypes representing three photoperiodic ecotypes, substantial
polymorphism was detected for at least one of the PHYB loci but not for the
PHYA locus. The novel character of the PHY family in black cottonwood, as
well as the differences in polymorphism we observed between the PHYA and
PHYB subfamilies, indicates that a number of fundamental macro- and
microevolutionary questions remain to be answered about the PHY family in
dicots.
相似文献
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Kaavya Krishna Kumar Moran Shalev-Benami Michael J. Robertson Hongli Hu Samuel D. Banister Scott A. Hollingsworth Naomi R. Latorraca Hideaki E. Kato Daniel Hilger Shoji Maeda William I. Weis David L. Farrens Ron O. Dror Sanjay V. Malhotra Brian K. Kobilka Georgios Skiniotis 《Cell》2019,176(3):448-458.e12
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138.
Felista L. Tansi Margarita P. Filatova Dmitri O. Koroev Olga M. Volpina Steffi Lange Christina Schumann Ulf K. Teichgräber Siegmund Reissmann Ingrid Hilger 《Journal of cellular biochemistry》2019,120(4):6528-6541
In the last three decades, many new cell-penetrating peptides (CPPs) were developed that exhibited enhanced cell selectivity. Thus, we aimed to validate the tumor cell selectivity of peptides from this new generation, namely fragments mini-crotamine and mini-maurocalcine. Both of these peptides are derived from venoms. Furthermore, we studied an analog of the classical CPP HIV-TAT(47-57) with alternating chirality of Arg residues. To allow covalent coupling of cargoes or fluorophores, a cysteine residue was introduced to the N-terminus of the synthesized peptides. The therapeutic antibody trastuzumab conjugated to different fluorescent dyes was used for internalization studies. Comparison of uptake efficiencies revealed that CPPs of the new generation are in contrast to MPG-peptides, nearly unable to internalize the noncovalently formed complexes with trastuzumab. Interestingly, the fluorescent derivative of the crotamine fragment was mainly observed in a subpopulation of breast cancer cells, whereas it was homogenously distributed in fibrosarcoma, colon cancer, and noncancerous endothelia cells. Thus, the fluorescent crotamine fragment reported herein is a potent theranostic tool for image-guided applications. This peptide can be used to pinpoint the level of heterogeneity present within tumors and aid in the generation of therapeutics that target heterogenic subpopulations. 相似文献
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