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11.
The common src homology region 2 domain of cytoplasmic signaling proteins is a positive effector of v-fps tyrosine kinase function. 总被引:28,自引:15,他引:13
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A conserved noncatalytic domain SH2 (for src homology region 2) is located immediately N terminal to the kinase domains of all cytoplasmic protein-tyrosine kinases. We found that the wild-type v-fps SH2 domain stimulated the enzymatic activity of the adjacent kinase domain 10-fold and functioned as a powerful positive effector of catalytic and transforming activities within the v-fps oncoprotein (P130gag-fps). Partial proteolysis of P130gag-fps and supporting genetic data indicated that the v-fps SH2 domain exerts its effect on catalytic activity through an intramolecular interaction with the kinase domain. Amino acid alterations in the SH2 domain that impaired kinase function interfered with association of the SH2 domain with the kinase domain. Deletion of a conserved octapeptide motif converted the v-fps SH2 domain from an activator to an inhibitor of tyrosine kinase activity. This latent inhibitory activity of v-fps SH2 has functional implications for phospholipase C-gamma and p21ras GTPase-activating protein, both of which have two distinct SH2 domains suggestive of complex regulation. In addition to regulating the specific activity of the kinase domain, the SH2 domain of P130gag-fps was also found to be required for the tyrosine phosphorylation of specific cellular proteins, notably polypeptides of 124 and 62 kilodaltons. The SH2 domain therefore appears to play a dual role in regulation of kinase activity and recognition of cellular substrates. 相似文献
12.
Shmuel Moran 《International journal of biometeorology》1989,33(2):101-108
Natural populations of the landsnailTheba pisana (Pulmonata: Helicidae) were studied in the Mediterranean coastal plains of Israel. The life cycle is annual. Egg-laying occurs in the winter and the descendants grow fast during the spring, except for a part of the population the ceases growing. These individuals, termed infantiles, retain immature size and shape and a rudimentary status of the genital system. The percentage of infantilism in the population is positively related to the density of the snail population in the winter, and is negatively related to the humidity of weather in the spring. A natural control mechanism ofT. pisana populations is proposed: (a) in a dense population of young snails infantilism prevents most of them from becoming parents and an over-sized population the following year; (b) in a humid spring a fall in the rate of infantilism enlarges the population size, thus compensating for reduced egg-laying in winter. 相似文献
13.
Detecting base pair substitutions in DNA fragments by temperature-gradient gel electrophoresis. 总被引:8,自引:3,他引:5
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A vertical gel electrophoresis apparatus is described which can distinguish DNA fragments differing by single base pair substitutions. The system employs a homogenous polyacrylamide gel containing urea-formamide and a temperature gradient which runs either perpendicular or parallel to the direction of electrophoresis. The temperature-gradient system simplifies several features of the denaturant-gradient system (1) and is relatively inexpensive to construct. Eight homologous 373 bp DNAs differing by one, two, or nine base pair substitutions were examined. DNA electrophoretic mobility changed abruptly with the temperature induced unwinding of DNA domains. GC to AT substitutions at different locations within the first melting domain, as well as an AT to TA transversion were separated with temperature gradients parallel to the electrophoretic direction. The relative stabilities of the DNAs observed in the gels were compared to predictions of DNA melting theory. General agreement was observed however complete correspondence was not obtained. 相似文献
14.
Novel hybrid maturases in unstable pseudorevertants of maturaseless mutants of yeast mitochondrial DNA. 总被引:5,自引:1,他引:4
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Unstable pseudorevertants of mitochondrial mutants of Saccharomyces cerevisiae lacking the maturase function encoded by the fourth intron of the cytochrome b gene (bI4) were isolated. They were found to be heteroplasmic cells owing their regained ability to respire (and grow on glycerol medium) to the presence of a rearranged (rho-) mtDNA that contains an in-frame fusion of the reading frames of the group I introns bI4 and intron 4 alpha of the coxl gene encoding subunit I of cytochrome c oxidase (aI4 alpha). The products of those gene fusions suppress the bI4 maturase deficiency still present in those heteroplasmic cells. Similar heteroplasmic pseudorevertants of a group II maturaseless mutant of the first intron of the coxI gene were characterized; they result from partial deletion of the coxI gene that fuses the reading frames of introns 1 and 2. These heteroplasms provide independent support for the existence of RNA maturases encoded by group I and group II introns. Also, since the petite/mit- heteroplasms arise spontaneously at very high frequencies they provide a system that can be used to obtain mutants unable to form or maintain heteroplasmic cells. 相似文献
15.
A large survey program was conducted during 1985/1986 to determine the extent of activity of the crown-of-thorns starfish, Acanthaster planci, and its broad effects on the coral communities of the Great Barrier Reef (GBR). The perimeters of 228 reefs (about 9% of reefs in the GBR system) were surveyed within 1 year using rapid survey, manta tow techniques. These reefs encompassed the broad latitudinal and longitudinal gradients within the GBR. Approximately 27% (62 reefs) of the reefs surveyed had recently experienced (18%), or were experiencing (9%), an outbreak of the crown-of-thorns starfish. These outbreaks were mainly confined to reefs in the central third of the GBR (between Lizard Island and Townsville) and had affected, to varying degrees, approximately 65% of the reefs surveyed within this region. A greater proportion of mid-shelf reefs had experienced outbreaks than outer-shelf reefs, although this difference was not statistically significant. Of the small number of inner-shelf reefs surveyed, none had been recently affected by an outbreak. Large active outbreaks of starfish were reported on many of the reefs located off Townsville while much smaller outbreaks were found on several reefs at the southern end of the GBR, in the Swain Reef complex. Almost 86% of reefs currently experiencing an outbreak had moderate to high coral mortality over at least a third of their perimeters. Only 10% of reefs with active outbreaks had high coral mortality over most of their windward and leeward margins. A similar proportion of reefs had low to moderate coral mortality over less than a third of their perimeters. 相似文献
16.
17.
B H Johnson R R Dean S M Moran E B Thompson 《The Journal of steroid biochemistry and molecular biology》1992,42(1):1-9
We have studied the growth effects of conditioned media, interleukin-2 and PGE prostaglandin analogs on the glucocorticoid-sensitive human leukemic T-cell clone, CEM-C7. After 4 days, the glucocorticoid dexamethasone at approximately 10 nM kills 50% of CEM-C7 cells. To test the hypothesis that glucocorticoid-mediated lymphocytolysis was due to suppression of lymphokine expression only, we attempted to protect CEM-C7 cells from lysis by provision of lymphokine(s). Conditioned media from interleukin-2 secreting Jurkat T-cells as well as the glucocorticoid-insensitive, but receptor positive clone, CEM-C1, failed to prevent lymphocytolysis; exogenous interleukin-2 also did not provide protection. There were complex, biphasic interactions between dexamethasone and the synthetic PGEs, enisoprost and enisoprost free acid. Low doses of enisoprost alone (0.01 to 1 microgram/ml) stimulated growth, and in combinations completely reversed the growth inhibitory effects of 10 nM dexamethasone. Higher concentrations of enisoprost were inherently lethal and were additive to the steroid effect. Thus the glucocorticoid-induced lymphocytolysis in this human leukemic T-cell line may be modified biphasically by PGE prostaglandins, depending on their concentration. However, interleukin-2 or components in the conditioned media assayed had no effect in ameliorating the lethal response to glucocorticoid. 相似文献
18.
Analysis with specific polyclonal antiserum indicates that the E1A-associated 300-kDa product is a stable nuclear phosphoprotein that undergoes cell cycle phase-specific modification. 总被引:21,自引:6,他引:15
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Binding of a 300-kDa host cell protein (p300) is tightly correlated with the ability of the adenovirus E1A products to induce quiescent baby rat kidney cells to proliferate. We have generated rabbit polyclonal antibodies against p300 to characterize this protein further. We have found p300 to be a nuclear phosphoprotein that is actively synthesized in both quiescent and proliferating baby rat kidney cells. In partially purified mitotic cell populations, we observe a form of p300 with decreased electrophoretic mobility in sodium dodecyl sulfate-polyacrylamide gels that shares a nearly identical partial proteolytic digest pattern with p300. The slower-migrating form of p300 is greatly reduced by treating immune complexes with potato acid phosphatase. The relative stability and presence of p300 even in resting cells suggests that p300 has a basal cell function, but the appearance of differentially modified forms during the cell cycle suggests the possibility that p300 function is modulated specifically in growing cells. 相似文献
19.
Characterization of the cloned BamHI restriction modification system: its nucleotide sequence, properties of the methylase, and expression in heterologous hosts. 总被引:16,自引:8,他引:8
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J E Brooks P D Nathan D Landry L A Sznyter P Waite-Rees C L Ives L S Moran B E Slatko J S Benner 《Nucleic acids research》1991,19(4):841-850
The BamHI restriction modification system was previously cloned into E. coli and maintained with an extra copy of the methylase gene on a high copy vector (Brooks et al., (1989) Nucl. Acids Res. 17, 979-997). The nucleotide sequence of a 3014 bp region containing the endonuclease (R) and methylase (M) genes has now been determined. The sequence predicts a methylase protein of 423 amino acids, Mr 49,527, and an endonuclease protein of 213 amino acids, Mr 24,570. Between the two genes is a small open reading frame capable of encoding a 102 amino acid protein, Mr 13,351. The M. BamHI enzyme has been purified from a high expression clone, its amino terminal sequence determined, and the nature of its substrate modification studied. The BamHI methylase modifies the internal C within its recognition sequence at the N4 position. Comparisons of the deduced amino acid sequence of M. BamHI have been made with those available for other DNA methylases: among them, several contain five distinct regions, 12 to 22 amino acids in length, of pronounced sequence similarity. Finally, stability and expression of the BamHI system in both E. coli and B. subtilis have been studied. The results suggest R and M expression are carefully regulated in a 'natural' host like B. subtilis. 相似文献
20.
E Dubnau J Weir G Nair L Carter rd C Moran Jr I Smith 《Journal of bacteriology》1988,170(3):1054-1062
The DNA sequences of the spo0H genes from Bacillus licheniformis and B. subtilis are described, and the predicted open reading frames code for proteins of 26,097 and 25,447 daltons, respectively. The two spo0H gene products are 91% identical to one another and about 25% identical to most of the procaryotic sigma factors. The predicted proteins have a conserved 14-amino-acid sequence at their amino terminal end, typical of sigma factors. Antibodies raised against the spo0H gene product of B. licheniformis specifically react with RNA polymerase sigma factor protein, sigma 30, purified from B. subtilis. We conclude that the spo0H genes of B. licheniformis and B. subtilis code for sigma 30, now known as sigma H. 相似文献