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P. J. Higgins 《Cellular and molecular life sciences : CMLS》1980,36(12):1388-1389
Summary Except for a markedly reduced anodal electrophoretic mobility, the serum albumin of the Galapagos marine iguana was physico-chemically identical to that of terrestrial iguanids. Reduction in albumin net charge may have facilitated the adaptation of this species to a semi-aquatic environment. 相似文献
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Peptide chemotaxis in E. coli involves the Tap signal transducer and the dipeptide permease 总被引:29,自引:0,他引:29
Bacterial chemotaxis provides a simple model system for the more complex sensory responses of multicellular eukaryotic organisms. In Escherichia coli, methylation and demethylation of four related membrane proteins, the methyl-accepting chemotaxis proteins (or MCPs), is central to chemotactic sensing and signal transduction. Three of these proteins, Tar, Tsr and Trg, have been assigned specific roles in chemotaxis. However, the role of the fourth MCP, Tap, has remained obscure. We demonstrate here that Tap functions as a conventional signal transducer, enabling the cell to respond chemotactically to dipeptides. This provides the first evidence of specific bacterial chemotaxis towards peptides. Peptide taxis requires the function of a periplasmic component of the dipeptide permease. This protein represents the first example of a periplasmic chemoreceptor that does not have a sugar substrate. 相似文献
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Structural model of ATP-binding proteins associated with cystic fibrosis, multidrug resistance and bacterial transport 总被引:111,自引:0,他引:111
S C Hyde P Emsley M J Hartshorn M M Mimmack U Gileadi S R Pearce M P Gallagher D R Gill R E Hubbard C F Higgins 《Nature》1990,346(6282):362-365
The ATP-binding cassette (ABC) superfamily of transport systems now includes over thirty proteins that share extensive sequence similarity and domain organization. This superfamily includes the well characterized periplasmic binding protein-dependent uptake systems of prokaryotes, bacterial exporters, and eukaryotic proteins including the P-glycoprotein associated with multidrug resistance in tumours (MDR), the STE6 gene product that mediates export of yeast a-factor mating pheromone, pfMDR that is implicated in chloroquine resistance of the malarial parasite, and the product of the cystic fibrosis gene (CFTR). Here we present a tertiary structure model of the ATP-binding cassettes characteristic of this class of transport system, based on similarities between the predicted secondary structures of members of this family and the previously determined structure of adenylate kinase. This model has implications for both the molecular basis of transport and cystic fibrosis and provides a framework for further experimentation. 相似文献
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本文针对当前宽带城域网的主流技术进行对照分析,设计出一个既能适应竞争形式需要、又能最大限度利用现有电信资源的宽带IP城域网,给出其整体设计原则和网络构架. 相似文献
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