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The receptor for transferrin on murine myeloma cells: one-step purification based on its physiology, and partial amino acid sequence 总被引:3,自引:0,他引:3
I R van Driel P A Stearne B Grego R J Simpson J W Goding 《Journal of immunology (Baltimore, Md. : 1950)》1984,133(6):3220-3224
The receptor for transferrin is one of the major surface proteins of proliferating lymphocytes and other cells. It binds ferrotransferrin from serum and endocytoses it into an acidic nonlysosomal intracellular compartment where iron is released, but in which apotransferrin remains tightly bound to its receptor. Recycling of the apotransferrin-receptor complex to the cell surface is associated with a return to neutral pH and concomitant loss of affinity of apotransferrin for its receptor. Apotransferrin is then free to leave the cell and initiate a new cycle. We have exploited this cycle in a novel method for the purification of the receptor for transferrin. Murine myeloma cells were lysed in nonionic detergent, and the lysate passed over a column of ferrotransferrin-agarose at pH 7.4. After washing with sodium acetate at pH 5.0, iron was removed with sodium citrate pH 5.0 and desferrioxamine. Upon returning the pH to neutrality, the receptor was eluted and found to be homogeneous by SDS-polyacrylamide gel electrophoresis under both reducing and nonreducing conditions. The degree of purification was estimated to be at least 3,000-fold, and the calculated yield was 10 to 20%. The purified receptor was capable of binding to transferrin. The receptor was digested with trypsin, and the resulting peptides were separated by reversed-phase high performance liquid chromatography in NH4HCO3. Selected peptides were rechromatographed in 0.1% trifluoroacetic acid, and their amino acid sequences were determined. 相似文献
876.
Five new species of Passiflora subgenera Plectostemma and Tacsonia from Ecuador are described, viz. P. discophora, P. monadelpha, P. subpurpurea, P. hirtiflora and P. sanctaebarbarae . Section Discophora of subg. Plectostemma is proposed. 相似文献
877.
New methods of analysing genetic data provide powerful tools for quantifying dispersal patterns and reconstructing population
histories. Here we examine the population structure of the bumblebee Bombus hortorum in a model island system, the Western Isles of Scotland, using microsatellite markers. Following declines in other species,
B. hortorum is the only remaining long-tongued bumblebee species found in much of Europe, and thus it is of particular ecological importance.
Our data suggest that populations of B. hortorum in western Scotland exist as distinct genetic clusters occupying groups of nearby islands. Population structuring was higher
than for other bumblebee species which have previously been studied in this same island group (Fst = 0.16). Populations showed significant isolation by distance. This relationship was greatly improved by using circuit theory
to allow dispersal rates to differ over different landscape features; as we would predict, sea appears to provide far higher
resistance to dispersal than land. Incorporating bathymetry data improved the fit of the model further; populations separated
by shallow seas are more genetically similar than those separated by deeper seas. We argue that this probably reflects events
following the last ice age when the islands were first colonized by this bee species (8,500–5,000 ybp), when the sea levels
were lower and islands separated by shallow channels would have been joined. In the absence of significant gene flow these
genetic clusters appear to have since diverged over the following 5,000 years and arguably may now represent locally adapted
races, some occurring on single islands. 相似文献
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An overview of research seeking and studying the potential low temperature sensors in plants is provided. It was shown that the number of potential candidates for low temperature sensors is quite wide and includes both individual intracellular structures and substances: membranes, cytoskeletal elements, chromatin, phytochromes, DNA, RNA, specific proteins, and sugars. It was noted that, depending on the mode of thermal exposure (intensity, cooling rate, duration, etc.), the leading role of temperature sensors may be played by different structures or substances. Apparently, this variety allows plants to respond to cold more flexibly and appropriately. 相似文献