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181.
Wood JM Culham DE Hillar A Vernikovska YI Liu F Boggs JM Keates RA 《Biochemistry》2005,44(15):5634-5646
Transporter ProP of Escherichia coli, a member of the major facilitator superfamily (MFS), acts as an osmosensor and an osmoregulator in cells and after purification and reconstitution in proteoliposomes. H(+)-osmoprotectant symport via ProP is activated when medium osmolality is elevated with membrane impermeant osmolytes. The three-dimensional structure of ProP was modeled with the crystal structure of MFS member GlpT as a template. This GlpT structure represents the inward (or cytoplasm)-facing conformation predicted by the alternating access model for transport. LacZ-PhoA fusion analysis and site-directed fluorescence labeling substantiated the membrane topology and orientation predicted by this model and most hydropathy analyses. The model predicts the presence of a proton pathway within the N-terminal six-helix bundle of ProP (as opposed to the corresponding pathway found within the C-terminal helix bundle of its paralogue, LacY). Replacement of residues within the N-terminal helix bundle impaired the osmotic activation of ProP, providing the first indication that residues outside the C-terminal domain are involved in osmosensing. Some residues that were accessible from the periplasmic side, as predicted by the structural model, were more susceptible to covalent labeling in permeabilized membrane fractions than in intact bacteria. These residues may be accessible from the cytoplasmic side in structures not represented by our current model, or their limited exposure in vivo may reflect constraints on transporter structure that are related to its osmosensory mechanism. 相似文献
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Doreen?Odom J.?A.?Sinden Oscar?Cacho G.?R.?GriffithEmail author 《Biological invasions》2005,7(3):445-457
Scotch broom (Cytisus scoparius, L.), is an exotic leguminous shrub, native to Europe, which invades pastoral and woodland ecosystems and adjoining river systems in cool, high rainfall regions of southeastern Australia. Broom has invaded 10,000ha of eucalypt woodland in Barrington Tops National Park in New South Wales, and is having a major impact on the natural ecology of the sub-alpine environment. It is extremely competitive with the native flora, retarding their growth and in many areas blanketing the ground and preventing growth of many understorey species in open forest areas. A number of rare and endangered species are believed to be under threat from this invasion. An active program to manage the threat is being implemented by the New South Wales National Parks and Wildlife Service. The management issues relevant to this threat are addressed through the application of a detailed bio-economic model of broom management. The results show that intervention in the management of broom in this natural ecosystem is clearly economically justified, and increases in the existing budgets appear to be justified. A combination of control measures, rather than any single measure, is almost always justified. Attempts to eradicate the broom invasion appear to be undesirable, so containment is the preferable strategy. Further, funding bodies should give assurances of future budget levels. The method of analysis reported here should be applicable to other types of biological invasions. 相似文献
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Dr. Doreen E. Ashhurst 《Cell and tissue research》1968,93(1):36-44
Summary The progressive effects of glycerol extraction on the myofibrils and membranous structures of insect flight muscle were examined. The myofibrils appear to be intact after extraction for several months. The mitochondria are completely disrupted within 3 days, but later the fragments come together to form mitochondrion-like bodies. The sarcoplasmic reticulum around the Z-lines is preserved for many months, but the T-system and dense bodies of the dyads disappear after about 7 days extraction.I am indebted to Professor J. W. S. Pringle, F.R.S. for his interest and helpful discussions throughout the course of this work. I should like to thank Miss Christine Williams for her technical assistance. 相似文献
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Doreen Tuhebwe James Bagonza Elizabeth Ekirapa Kiracho Adoke Yeka Alison M. Elliott Fred Nuwaha 《PloS one》2015,10(4)