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排序方式: 共有525条查询结果,搜索用时 15 毫秒
1.
A Merlin W Voos A C Maarse M Meijer N Pfanner J Rassow 《The Journal of cell biology》1999,145(5):961-972
Tim44 is a protein of the mitochondrial inner membrane and serves as an adaptor protein for mtHsp70 that drives the import of preproteins in an ATP-dependent manner. In this study we have modified the interaction of Tim44 with mtHsp70 and characterized the consequences for protein translocation. By deletion of an 18-residue segment of Tim44 with limited similarity to J-proteins, the binding of Tim44 to mtHsp70 was weakened. We found that in the yeast Saccharomyces cerevisiae the deletion of this segment is lethal. To investigate the role of the 18-residue segment, we expressed Tim44Delta18 in addition to the endogenous wild-type Tim44. Tim44Delta18 is correctly targeted to mitochondria and assembles in the inner membrane import site. The coexpression of Tim44Delta18 together with wild-type Tim44, however, does not stimulate protein import, but reduces its efficiency. In particular, the promotion of unfolding of preproteins during translocation is inhibited. mtHsp70 is still able to bind to Tim44Delta18 in an ATP-regulated manner, but the efficiency of interaction is reduced. These results suggest that the J-related segment of Tim44 is needed for productive interaction with mtHsp70. The efficient cooperation of mtHsp70 with Tim44 facilitates the translocation of loosely folded preproteins and plays a crucial role in the import of preproteins which contain a tightly folded domain. 相似文献
2.
Coronin, an actin binding protein of Dictyostelium discoideum localized to cell surface projections, has sequence similarities to G protein beta subunits. 总被引:6,自引:0,他引:6
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A soluble actin binding protein of Dictyostelium discoideum cells has been extracted and purified from precipitated actin-myosin complexes. This protein with a relative molecular mass of 55 kDa has been named coronin because of its association with crown-shaped cell surface projections of growth-phase D. discoideum cells. In aggregating cells, which respond most sensitively to the chemoattractant cyclic AMP, coronin is accumulated at the front where surface projections are directed towards a cAMP source. Since these cells can quickly change shape and polarity, it follows that coronin is rapidly reshuffled within the cells during motion and chemotactic orientation. The cDNA derived sequence of coronin indicates a protein of 49 kDa, consisting of an amino-terminal domain with similarities to the beta subunits of G proteins and a carboxy-terminal domain with a high tendency for alpha-helical structure. It is hypothesized that coronin is implicated in the transmission of chemotactic signals from cAMP receptors in the plasma membrane through G proteins to the cortical cytoskeleton, whose structure and activity is locally modulated. 相似文献
3.
Serge Fermandjian Constantin Sakarellos Franlois Piriou Michel Juy Flavio Toma Hung Lam Thanh Karl Lintner Mahesh C. Khosla Robert R. Smeby F. Merlin Bumpus 《Biopolymers》1983,22(1):227-231
The conformation–biological activity relationships in a series of angiotensin II analogs substituted in position 5 were studied. Results indicated that only analogs with β-branched residue in position 5 possess spectral and biological properties identical to that of parent angiotensin II. 相似文献
4.
Interferon-induced 56,000 Mr protein and its mRNA in human cells: molecular cloning and partial sequence of the cDNA. 总被引:25,自引:2,他引:23
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Treatment of responsive cells by interferons (IFNs) induces within a few hours a rise in the concentration of several proteins and mRNAs. In order to characterize these IFN-induced mRNA species, we have cloned in E. coli the cDNA made from a 17-18S poly(A)+ RNA of human fibroblastoid cells (SV80) treated with IFN-beta. We describe here a pBR322 recombinant plasmid (C56) which contains a 400 bp cDNA insert corresponding to a 18S mRNA species newly induced by IFN. The C56 mRNA codes for a 56,000 dalton protein easily detectable by hybridization-translation experiments. The sequence of 66 of the carboxy-terminal amino-acids of the protein can be deduced from the cDNA sequence. IFNs-alpha, beta or gamma are able to activate the expression of this gene in human fibroblasts as well as lymphoblastoid cells. The mRNA is not detectable without IFN; it reaches maximum levels (0.1% of the total poly(A)+ RNA) within 4-8 hrs and decreases after 16 hrs. 相似文献
5.
6.
Chemical cues produced by conspecific larvae deter oviposition by the coccidophagous ladybird beetle, Cryptolaemus montrouzieri 总被引:1,自引:0,他引:1
Experimental evidence shows that oviposition in Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) is deterred by the presence of conspecific larvae. A similar deterrent effect is also recorded when females are tested in an experimental set up that previously housed conspecific larvae. It is shown that an oviposition-deterring pheromone is associated with the abundant wax filaments produced by the larvae of C. montrouzieri. 相似文献
7.
L. Schreiber H.-W. Breiner M. Riederer M. Düggelin R. Guggenheim 《Plant biology (Stuttgart, Germany)》1994,107(5):353-361
The root endodermis of Clivia miniata Reg. was successfully isolated using the cell wall degrading enzymes cellulase and pectinase. The enzymes did not depolymerize those regions of the primary cell walls of anticlinal endodermal root cells where the Casparian strips were located. Since the endodermis of C. miniata roots remained in its primary developmental state over the whole root length, endodermal isolates essentially represented Casparian strips. Thus, sufficient amounts of isolated Casparian strips could be obtained to allow further detailed investigations of the isolates by microscopic, histochemical and analytical methods. Scanning electron microscopy revealed the reticular structure of the Casparian strips completely surrounding the central cylinder of the roots. Whereas in younger parts of the root only the anticlinal cell walls of the endodermis remained intact in the isolates, in older parts of the root the periclinal walls also restricted enzymatic degradation due to the deposition of lignin. Extracts of the isolates with organic solvents did not reveal any wax-like substances which might have been deposited within the cell wall forming a transport barrier, as is the case with cutin and suberin. However, several histochemical and analytical methods (elemental analysis and FTIR spectroscopy) showed that the chemical nature of the Casparian strips of C. miniata roots can definitely be a lignified cell wall. These findings are in complete agreement with studies carried out at the beginning of this century on the chemical nature of the Casparian strips of several other plant species. The implications of these results concerning apoplasmatic transport of solutes and water across Casparian strips are discussed. 相似文献
8.
9.
The effects of salinity, temperature, and N-fertilization on growth and yield of Rhodes grass were investigated. High levels of all three factors had a negative effect on tillering and consequently on the total yield. Though high salt-stress lowered the yields, it also lowered the content of free-NO3
– in the shoots, thus, raising the quality of the crops obtained.In partial fulfillment of the requirements for the degree of M.Sc. at The Tel Aviv University.In partial fulfillment of the requirements for the degree of M.Sc. at The Tel Aviv University. 相似文献
10.
Pertussis toxin administered to rats resulted in a polyuric state that was due to enhanced renal water excretion. Pertussis toxin also induced a defect in renal water conservation. These abnormalities in renal water excretion could not be attributed to polydipsia, impaired synthesis and/or release of arginine vasopressin or renal tubular dysfunction with solute diuresis. No evidence of pertussis toxin-induced renal tubular damage was present. These results indicate that pertussis toxin induces nephrogenic diabetes insipidus and this defect occurs at the level of the renal collecting tubule. 相似文献