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排序方式: 共有90条查询结果,搜索用时 424 毫秒
1.
Identification of a novel human Rho protein with unusual properties: GTPase deficiency and in vivo farnesylation. 总被引:20,自引:3,他引:17
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R Foster K Q Hu Y Lu K M Nolan J Thissen J Settleman 《Molecular and cellular biology》1996,16(6):2689-2699
We have identified a human Rho protein, RhoE, which has unusual structural and biochemical properties that suggest a novel mechanism of regulation. Within a region that is highly conserved among small GTPases, RhoE contains amino acid differences specifically at three positions that confer oncogenicity to Ras (12, 59, and 61). As predicted by these substitutions, which impair GTP hydrolysis in Ras, RhoE binds GTP but lacks intrinsic GTPase activity and is resistant to Rho-specific GTPase-activating proteins. Replacing all three positions in RhoE with conventional amino acids completely restores GTPase activity. In vivo, RhoE is found exclusively in the GTP-bound form, suggesting that unlike previously characterized small GTPases, RhoE may be normally maintained in an activated state. Thus, amino acid changes in Ras that are selected during tumorigenesis have evolved naturally in this Rho protein and have similar consequences for catalytic function. All previously described Rho family proteins are modified by geranylgeranylation, a lipid attachment required for proper membrane localization. In contrast, the carboxy-terminal sequence of RhoE predicts that, like Ras proteins, RhoE is normally farnesylated. Indeed, we have found that RhoE in farnesylated in vivo and that this modification is required for association with the plasma membrane and with an unidentified cellular structure that may play a role in adhesion. Thus, two unusual structural features of this novel Rho protein suggest a striking evolutionary divergence from the Rho family of GTPases. 相似文献
2.
Calcium content and distribution as a function of growth and transformation in the mouse 3T3 cell
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Total Ca content and that fraction of Ca sensitive to removal by the chelator ethylene glycol-bis(β-aminoethyl ether)N,N,N',N'-tetraacetate (EGTA) have been investigated in the mouse 3T3 cell as a function of growth stage, transformation with SV40 virus, and serum levels of the media. Cells were allowed to grow through several doublings in media containing (45)Ca. The cellular content of (45)Ca was used to access total cell Ca. That fraction of (45)Ca removed by EGTA was presumed to represent primarily surface-localized Ca. The data are expressed on a per cell volume basis to compensate for size differences as a function of growth stage and transformation. During exponential growth phase, the 3T3 cell contains 525pmol Ca/μl cell volume. Of this, approx. 457 pmol/μl is not removable by EGTA and, presumably, is cytoplasmically located. This value is in close agreement with previous studies on the HeLa cell (470 pmol Ca/μl cell water after the removal of the surface Ca). The low level of EGTA- removable Ca present in the 3T3 cell during early exponential growth (68 pmol Ca/μl cell volume) increases progressively with increasing cell density, and upon quiescence it is sevenfold greater. In contrast, SV40- transformed 3T3 cells growing exponentially possess total levels of Ca which are approximately two-thirds the levels of the normal 3T3 cell. However, their EGTA-sensitive Ca is not significantly different from that of exponentially growing, normal 3T3 cells. As the transformed cells continue to grow at high density, their total ca and their sensitivity to EGTA do not change, in contrast to the normal 3T3 cell. Thus, an increase in Ca associated with the cell surface appears to be correlated with growth inhibition. This has been investigated further by regulating growth of the normal and transformed cell with alterations in the serum level of the media. In 4 percent calf serum the normal cell is stopped from continued proliferation. Growth stoppage under these conditions is characterized by a nearly fourfold increase in EGTA-removable Ca, similar to the increase observed upon quiescence in depleted 10 percent serum. Similar treatment of the transformed cell does not reduce its growth rate, nor does it significantly alter Ca distribution. However, at 0.5 percent medium serum levels, the SV40 3T3 growth rate is substantially reduced and, under these conditions, EGTA-removable Ca increases twofold. 相似文献
3.
The internal pH value (pHi) of the long-slender bloodstream form of Trypanosoma brucei was estimated from the distribution of 14C-labeled 5,5-dimethyl-2,4-oxazolidinedione or 14C-labeled methyl amine between the intracellular space of the cells and the medium. The pHi of T. brucei remained relatively constant at 7.0-7.2 throughout an extracellular pH (pHo) range of 6.0-8.0. The maintenance of an internal pH more acidic than the environment appears to be a unique feature. Preincubation of T. brucei with carbonyl cyanide m-chlorophenyl hydrazone (CCCP) or CCCP + valinomycin had no appreciable effect on the delta pH across the T. brucei membrane when the external pH was 8.0. However, when the external pH was 6.0, CCCP abolished the observed delta pH. Nigericin significantly dissipated the delta pH across the T. brucei membrane at all pHo values. These data suggest that under physiological conditions, the maintenance of a delta pH across the bloodstream-form T. brucei membrane may be by a mechanism other than an energy-dependent gradient, whereas an energy-dependent pump may be needed for maintaining the pHi in an acidic environment. The electrical potential (delta psi) across the trypanosomal plasma membrane was also estimated using the lipophilic cation, [3H]tetraphenyl-phosphonium bromide. It appears dependent on both the external pH and the external salt conditions. Under ionic conditions similar to the host bloodstream, it ranges from -76 to -160 mV over an external pH range of 6.0 to 8.0, with an estimated value of -155.5 +/- 0.7 at the physiological pH.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
4.
Harper AL von Gesjen SE Linford AS Peterson MP Faircloth RS Thissen MM Brusslan JA 《Photosynthesis research》2004,79(2):149-159
Plants can change the size of their light harvesting complexes in response to growth at different light intensities. Although these changes are small compared to those observed in algae, their conservation in many plant species suggest they play an important role in photoacclimation. A polyclonal antibody to the C-terminus of the Arabidopsis thaliana chlorophyllide a oxygenase (CAO) protein was used to determine if CAO protein levels change under three conditions which perturb chlorophyll levels. These conditions were: (1) transfer to shaded light intensity; (2) limited chlorophyll synthesis, and (3) during photoinhibition. Transfer of wild-type plants from moderate to shaded light intensity resulted in a slight reduction in the Chl a/b ratio, and increases in both CAO and Lhcb1 mRNA levels as well as CAO protein levels. CAO protein levels were also measured in the cch1 mutant, a P642L missense mutation in the H subunit of Mg-chelatase. This mutant has reduced total Chl levels and an increased Chl a/b ratio when transferred to moderate light intensity. After transfer to moderate light intensity, CAO mRNA levels decreased in the cch1 mutant, and a concomitant decrease in CAO protein levels was also observed. Measurements of tetrapyrrole intermediates suggested that decreased Chl synthesis in the cch1 mutant was not a result of increased feedback inhibition at higher light intensity. When wild-type plants were exposed to photoinhibitory light intensity for 3 h, total Chl levels decreased and both CAO mRNA and CAO protein levels were also reduced. These results indicate that CAO protein levels correlate with CAO mRNA levels, and suggest that changes in Chl b levels in vascular plants, are regulated, in part, at the CAO mRNA level. 相似文献
5.
Lai CM Yu MJ Brankov M Barnett NL Zhou X Redmond TM Narfstrom K Rakoczy PE 《Genetic vaccines and therapy》2004,2(1):3
Background
Leber's congenital amaurosis (LCA) is a severe form of retinal dystrophy. Mutations in the RPE65 gene, which is abundantly expressed in retinal pigment epithelial (RPE) cells, account for approximately 10–15% of LCA cases. In this study we used the high turnover, and rapid breeding and maturation time of the Rpe65 -/- knockout mice to assess the efficacy of using rAAV-mediated gene therapy to replace the disrupted RPE65 gene. The potential for rAAV-mediated gene treatment of LCA was then analyzed by determining the pattern of RPE65 expression, the physiological and histological effects that it produced, and any improvement in visual function. 相似文献6.
Rose E Staats R Thissen U Otten JE Schmelzeisen R Jonas I 《Plastic and reconstructive surgery》2002,110(2):392-396
Sleep-disordered breathing is frequently associated with children presenting congenital midface defects. Because of structural and functional anomalies in the upper airway, children with cleft palate, especially after surgery, may carry a higher risk of developing sleep-disordered breathing. However, the presence of such sleep-disordered breathing in older cleft palate children has not been emphasized. The aim of this comparative overnight cardiorespiratory sleep study was to evaluate cleft palate patients according to sleep-disordered breathing. A group of 43 cleft palate children (17 girls and 26 boys; mean age, 12.1 +/- 3.8 years) was compared with a control group of 20 randomly selected, noncleft children matched for age, sex, and body mass index. None of the patients suffered from manifest sleep-disordered breathing. Cleft palate patients had a statistically significantly higher respiratory disturbance index and snoring index, but no increased apnea index. The data suggest that cleft palate patients having undergone primary closure of the palate demonstrate microsymptoms of nocturnal upper airway obstruction. 相似文献
7.
Krens FA Schaart JG Groenwold R Walraven AE Hesselink T Thissen JT 《Transgenic research》2011,20(5):1113-1123
Introduction of sustainable scab resistance in elite apple cultivars is of high importance for apple cultivation when aiming
at reducing the use of chemical crop protectants. Genetic modification (GM) allows the rapid introduction of resistance genes
directly into high quality apple cultivars. Resistance genes can be derived from apple itself but genetic modification also
opens up the possibility to use other, non-host resistance genes. A prerequisite for application is the long-term performance
and stability of the gene annex trait in the field. For this study, we produced and selected a series of transgenic apple
lines of two cultivars, i.e. ‘Elstar’ and ‘Gala’ in which the barley hordothionin gene (hth) was introduced. After multiplication, the GM hth-lines, non-GM susceptible and resistant controls and GM non-hth controls were planted in a random block design in a field trial in 40 replicates. Scab resistance was monitored after artificial
inoculation (first year) and after natural infection (subsequent years). After the trial period, the level of expression of
the hth gene was checked by quantitative RT-PCR. Four of the six GM hth apple lines proved to be significantly less susceptible to apple scab and this trait was found to be stable for the entire
4-year period. Hth expression at the mRNA level was also stable. 相似文献
8.
Urotensin II (UII) and urocortin (UCN) are potent contributors to the physiopathology of heart failure. Our study investigated the effects of UII and UCN on the expression of myostatin (Mstn) in primary culture of adult cardiomyocytes. Adult rat cardiomyocytes were stimulated for 48 h with UII and UCN. Cell size and protein content were determined. Mstn gene expression was determined by real time quantitative polymerase chain reaction. Treatment with UII and UCN stimulates hypertrophy of adult cardiomyocytes. This effect was associated with a twofold increase of Mstn gene expression. We have established for the first time that the two hypertrophic peptides UII and UCN stimulate the expression of Mstn. 相似文献
9.
10.