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991.
992.
A cooperative action of the ATP-dependent import motor complex and the inner membrane potential drives mitochondrial preprotein import
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The import of mitochondrial preproteins requires an electric potential across the inner membrane and the hydrolysis of ATP in the matrix. We assessed the contributions of the two energy sources to the translocation driving force responsible for movement of the polypeptide chain through the translocation channel and the unfolding of preprotein domains. The import-driving activity was directly analyzed by the determination of the protease resistances of saturating amounts of membrane-spanning translocation intermediates. The ability to generate a strong translocation-driving force was solely dependent on the activity of the ATP-dependent import motor complex in the matrix. For a sustained import-driving activity on the preprotein in transit, an unstructured N-terminal segment of more than 70 to 80 amino acid residues was required. The electric potential of the inner membrane was required to maintain the import-driving activity at a high level. The electrophoretic force of the potential exhibited only a limited capacity to unfold preprotein domains. We conclude that the membrane potential increases the probability of a dynamic interaction of the preprotein with the import motor. Polypeptide translocation and unfolding are mainly driven by the inward-directed translocation activity based on the functional cooperation of the import motor components. 相似文献
993.
Lee KY Jeong JW Wang J Ma L Martin JF Tsai SY Lydon JP DeMayo FJ 《Molecular and cellular biology》2007,27(15):5468-5478
The process of implantation, necessary for all viviparous birth, consists of tightly regulated events, including apposition of the blastocyst, attachment to the uterine lumen, and differentiation of the uterine stroma. In rodents and primates the uterine stroma undergoes a process called decidualization. Decidualization, the process by which the uterine endometrial stroma proliferates and differentiates into large epithelioid decidual cells, is critical to the establishment of fetal-maternal communication and the progression of implantation. The role of bone morphogenetic protein 2 (Bmp2) in regulating the transformation of the uterine stroma during embryo implantation in the mouse was investigated by the conditional ablation of Bmp2 in the uterus using the (PR-cre) mouse. Bmp2 gene ablation was confirmed by real-time PCR analysis in the PR-cre; Bmp2fl/fl (termed Bmp2d/d) uterus. While littermate controls average 0.9 litter of 6.2+/-0.7 pups per month, Bmp2d/d females are completely infertile. Analysis of the infertility indicates that whereas embryo attachment is normal in the Bmp2d/d as in control mice, the uterine stroma is incapable of undergoing the decidual reaction to support further embryonic development. Recombinant human BMP2 can partially rescue the decidual response, suggesting that the observed phenotypes are not due to a developmental consequence of Bmp2 ablation. Microarray analysis demonstrates that ablation of Bmp2 leads to specific gene changes, including disruption of the Wnt signaling pathway, Progesterone receptor (PR) signaling, and the induction of prostaglandin synthase 2 (Ptgs2). Taken together, these data demonstrate that Bmp2 is a critical regulator of gene expression and function in the murine uterus. 相似文献
994.
Choi IY Kim SJ Jeong HJ Park SH Song YS Lee JH Kang TH Park JH Hwang GS Lee EJ Hong SH Kim HM Um JY 《Molecular and cellular biochemistry》2007,305(1-2):153-161
The citrus unshiu peel has been used traditionally as a medicine to improve bronchial and asthmatic conditions or cardiac
and blood circulation in Korea, China, and Japan. Here, we report the effects of citrus unshiu peel water extract (CPWE) on
the phorbol myristate acetate (PMA) + calcium ionophore A23187-induced hypoxia-inducible factor-1α (HIF-1α) activation and
inflammatory cytokine production from the human mast cell line, HMC-1 cells. We compared CPWE with hesperidin, a common constituent
of citrus unshiu. CPWE and hesperidin inhibited the PMA + A23187-induced HIF-1α expression and the subsequent production of
vascular endothelial growth factor (VEGF). In addition, CPWE suppressed PMA + A23187-induced phosphorylation of the extracellular
signal-regulated kinase (ERK). We also show that the increased cytokines interleukin (IL)-1β, IL-8, and tumor necrosis factor
(TNF)-α level was significantly inhibited by treatment of CPWE or hesperidin. In the present study, we report that CPWE and
hesperidin are inhibitors of HIF-1α and cytokines on the mast cell-mediated inflammatory responses. 相似文献
995.
Soucy KG Lim HK Benjo A Santhanam L Ryoo S Shoukas AA Vazquez ME Berkowitz DE 《Radiation and environmental biophysics》2007,46(2):179-186
Irradiation of the heart and vasculature can cause a spectrum of cardiovascular complications, including increased risk of
myocardial infarction or coronary heart disease. Although irradiation is implicated in oxidant stress and chronic inflammation,
the underlying molecular mechanisms have not been elucidated. We tested the hypothesis that irradiation-initiated upregulation
of xanthine oxidase (XO), a primary source of cardiovascular reactive oxygen species, contributes to endothelial dysfunction
and increased vascular stiffness. Twenty-two, 3-month-old Sprague–Dawley male rats were gamma-irradiated at the following
doses: 0, 50, 160, and 500 cGy. Rats exposed to 500 cGy showed a significant increase in endothelial XO expression and a twofold
increase in XO activity, compared to the 0 cGy controls. Endothelial function was investigated ex vivo through vascular tension
dose–responses to the endothelial dependent vasodilator, acetylcholine. Endothelial-dependent relaxation in aorta of the 500 cGy
exposed rats was significantly attenuated from the control group. Remarkably, specific inhibition of XO with oxypurinol restored
the relaxation response to that of the control. Furthermore, these ex vivo results are reflected in vivo through alterations
in vascular stiffness, as measured by pulse wave velocity (PWV). As early as 1-day post-exposure, rats exhibited a significant
increase in PWV from pre-exposure. The PWV of irradiated rats (50, 160, and 500 cGy) were greater than those of 0 cGy control
rats at 1 day, 1 and 2 weeks. The sham and irradiated rats possessed equivalent pre-exposure PWV, with sham showing no change
over 2 weeks. Thus, these findings suggest that early upregulation of XO contributes to oxidative stress and endothelial nitro-redox
imbalance with resultant endothelial dysfunction and altered vascular mechanics. Furthermore, these data identify XO as a
potential molecular target for attenuating irradiation-induced cardiovascular injury. 相似文献
996.
997.
998.
999.
Frequency of Secondary Symbiont Infection in an Invasive Psyllid Relates to Parasitism Pressure on a Geographic Scale in California 总被引:3,自引:2,他引:1
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Two endosymbionts, an obligate primary symbiont and a facultative secondary symbiont, are harbored within the invasive red gum (eucalyptus) lerp psyllid, Glycaspis brimblecombei, in California. An extensive survey of diversity and frequency of G. brimblecombei's secondary symbiont in multiple populations throughout the state of California was conducted using PCR detection, restriction enzymes, cloning, and sequencing. A total of 380 G. brimblecombei individuals in 19 populations were screened for secondary symbionts. Based on molecular screening results, only one type of secondary symbiont was present in G. brimblecombei populations in California. Overall, 40% of the 380 psyllids screened were infected with the secondary symbiont. Interestingly, secondary symbiont infection frequencies in G. brimblecombei populations varied dramatically from 0 to 75% and were significantly related to parasitism pressure by Psyllaphaegus bliteus, a solitary endoparasitoid of the psyllid. 相似文献
1000.
Construction and Characterization of Shuttle Vectors for Succinic Acid-Producing Rumen Bacteria 总被引:2,自引:0,他引:2
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Yu-Sin Jang Young Ryul Jung Sang Yup Lee Ji Mahn Kim Jeong Wook Lee Doo-Byoung Oh Hyun Ah Kang Ohsuk Kwon Seh Hee Jang Hyohak Song Sang Jun Lee Kyu Young Kang 《Applied microbiology》2007,73(17):5411-5420
Shuttle vectors carrying the origins of replication that function in Escherichia coli and two capnophilic rumen bacteria, Mannheimia succiniciproducens and Actinobacillus succinogenes, were constructed. These vectors were found to be present at ca. 10 copies per cell. They were found to be stably maintained in rumen bacteria during the serial subcultures in the absence of antibiotic pressure for 216 generations. By optimizing the electroporation condition, the transformation efficiencies of 3.0 × 106 and 7.1 × 106 transformants/μg DNA were obtained with M. succiniciproducens and A. succinogenes, respectively. A 1.7-kb minimal replicon was identified that consists of the rep gene, four iterons, A+T-rich regions, and a dnaA box. It was found that the shuttle vector replicates via the theta mode, which was confirmed by sequence analysis and Southern hybridization. These shuttle vectors were found to be suitable as expression vectors as the homologous fumC gene encoding fumarase and the heterologous genes encoding green fluorescence protein and red fluorescence protein could be expressed successfully. Thus, the shuttle vectors developed in this study should be useful for genetic and metabolic engineering of succinic acid-producing rumen bacteria. 相似文献