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Laura J. Mares Alvaro Garcia Helge H. Rasmussen Flemming Cornelius Yasser A. Mahmmoud Joshua R. Berlin Bogdan Lev Toby W. Allen Ronald J. Clarke 《Biophysical journal》2014
The charge-transporting activity of the Na+,K+-ATPase depends on its surrounding electric field. To isolate which steps of the enzyme’s reaction cycle involve charge movement, we have investigated the response of the voltage-sensitive fluorescent probe RH421 to interaction of the protein with BTEA (benzyltriethylammonium), which binds from the extracellular medium to the Na+,K+-ATPase’s transport sites in competition with Na+ and K+, but is not occluded within the protein. We find that only the occludable ions Na+, K+, Rb+, and Cs+ cause a drop in RH421 fluorescence. We conclude that RH421 detects intramembrane electric field strength changes arising from charge transport associated with conformational changes occluding the transported ions within the protein, not the electric fields of the bound ions themselves. This appears at first to conflict with electrophysiological studies suggesting extracellular Na+ or K+ binding in a high field access channel is a major electrogenic reaction of the Na+,K+-ATPase. All results can be explained consistently if ion occlusion involves local deformations in the lipid membrane surrounding the protein occurring simultaneously with conformational changes necessary for ion occlusion. The most likely origin of the RH421 fluorescence response is a change in membrane dipole potential caused by membrane deformation. 相似文献
37.
Relations in biomedical ontologies 总被引:5,自引:0,他引:5
Smith B Ceusters W Klagges B Köhler J Kumar A Lomax J Mungall C Neuhaus F Rector AL Rosse C 《Genome biology》2005,6(5):R46-15
To enhance the treatment of relations in biomedical ontologies we advance a methodology for providing consistent and unambiguous formal definitions of the relational expressions used in such ontologies in a way designed to assist developers and users in avoiding errors in coding and annotation. The resulting Relation Ontology can promote interoperability of ontologies and support new types of automated reasoning about the spatial and temporal dimensions of biological and medical phenomena. 相似文献
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Donnelly MJ McCall PJ Lengeler C Bates I D'Alessandro U Barnish G Konradsen F Klinkenberg E Townson H Trape JF Hastings IM Mutero C 《Malaria journal》2005,4(1):12-5
There are already 40 cities in Africa with over 1 million inhabitants and the United Nations Environmental Programme estimates that by 2025 over 800 million people will live in urban areas. Recognizing that malaria control can improve the health of the vulnerable and remove a major obstacle to their economic development, the Malaria Knowledge Programme of the Liverpool School of Tropical Medicine and the Systemwide Initiative on Malaria and Agriculture convened a multi-sectoral technical consultation on urban malaria in Pretoria, South Africa from 2nd to 4th December, 2004. The aim of the meeting was to identify strategies for the assessment and control of urban malaria. This commentary reflects the discussions held during the meeting and aims to inform researchers and policy makers of the potential for containing and reversing the emerging problem of urban malaria. 相似文献
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Orth D Grif K Fisher I Fruth A Tschäpe H Scheutz F Dierich MP Würzner R 《Current microbiology》2006,53(5):428-429
Novel and as yet rare non-O157 Shiga toxin (Stx)-producing Escherichia coli (STEC) serotypes are emerging in Europe. Two different sorbitol-fermenting STECs, O100:H- carrying the virulence gene stx2 and O127:H40 carrying stx1 and eae genes (found in two related subjects), were isolated from patients’ stool samples. Non-O157 STEC infections in humans are
currently under-diagnosed. This report highlights the need for, and importance of, screening for Shiga toxins or serotypes
other than just O157. 相似文献
40.
Based on the high-resolution X-ray crystallographic structure of phospholipase C from Bacillus cereus, the orientation of the phosphatidylcholine substrate in the active site of the enzyme is proposed. The proposal is based on extensive calculations using the GRID program and molecular mechanics geometry relaxations. The substrate model has been constructed by successively placing phosphate, choline and diacylglycerol moieties in the positions indicated from GRID calculations. On the basis of the resulting orientation of a complete phosphatidylcholine molecule, we propose a mechanism for the hydrolysis of the substrate. 相似文献