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Abrescia NG Cockburn JJ Grimes JM Sutton GC Diprose JM Butcher SJ Fuller SD San Martín C Burnett RM Stuart DI Bamford DH Bamford JK 《Nature》2004,432(7013):68-74
The structure of the membrane-containing bacteriophage PRD1 has been determined by X-ray crystallography at about 4 A resolution. Here we describe the structure and location of proteins P3, P16, P30 and P31. Different structural proteins seem to have specialist roles in controlling virus assembly. The linearly extended P30 appears to nucleate the formation of the icosahedral facets (composed of trimers of the major capsid protein, P3) and acts as a molecular tape-measure, defining the size of the virus and cementing the facets together. Pentamers of P31 form the vertex base, interlocking with subunits of P3 and interacting with the membrane protein P16. The architectural similarities with adenovirus and one of the largest known virus particles PBCV-1 support the notion that the mechanism of assembly of PRD1 is scaleable and applies across the major viral lineage formed by these viruses. 相似文献
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Cockburn JJ Abrescia NG Grimes JM Sutton GC Diprose JM Benevides JM Thomas GJ Bamford JK Bamford DH Stuart DI 《Nature》2004,432(7013):122-125
Membranes are essential for selectively controlling the passage of molecules in and out of cells and mediating the response of cells to their environment. Biological membranes and their associated proteins present considerable difficulties for structural analysis. Although enveloped viruses have been imaged at about 9 A resolution by cryo-electron microscopy and image reconstruction, no detailed crystallographic structure of a membrane system has been described. The structure of the bacteriophage PRD1 particle, determined by X-ray crystallography at about 4 A resolution, allows the first detailed analysis of a membrane-containing virus. The architecture of the viral capsid and its implications for virus assembly are presented in the accompanying paper. Here we show that the electron density also reveals the icosahedral lipid bilayer, beneath the protein capsid, enveloping the viral DNA. The viral membrane contains about 26,000 lipid molecules asymmetrically distributed between the membrane leaflets. The inner leaflet is composed predominantly of zwitterionic phosphatidylethanolamine molecules, facilitating a very close interaction with the viral DNA, which we estimate to be packaged to a pressure of about 45 atm, factors that are likely to be important during membrane-mediated DNA translocation into the host cell. In contrast, the outer leaflet is enriched in phosphatidylglycerol and cardiolipin, which show a marked lateral segregation within the icosahedral asymmetric unit. In addition, the lipid headgroups show a surprising degree of order. 相似文献
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AG Henry PS Ungar BH Passey M Sponheimer L Rossouw M Bamford P Sandberg DJ de Ruiter L Berger 《Nature》2012,487(7405):90-93
Specimens of Australopithecus sediba from the site of Malapa, South Africa (dating from approximately 2 million years (Myr) ago) present a mix of primitive and derived traits that align the taxon with other Australopithecus species and with early Homo. Although much of the available cranial and postcranial material of Au. sediba has been described, its feeding ecology has not been investigated. Here we present results from the first extraction of plant phytoliths from dental calculus of an early hominin. We also consider stable carbon isotope and dental microwear texture data for Au. sediba in light of new palaeoenvironmental evidence. The two individuals examined consumed an almost exclusive C(3) diet that probably included harder foods, and both dicotyledons (for example, tree leaves, fruits, wood and bark) and monocotyledons (for example, grasses and sedges). Like Ardipithecus ramidus (approximately 4.4 Myr ago) and modern savanna chimpanzees, Au. sediba consumed C(3) foods in preference to widely available C(4) resources. The inferred consumption of C(3) monocotyledons, and wood or bark, increases the known variety of early hominin foods. The overall dietary pattern of these two individuals contrasts with available data for other hominins in the region and elsewhere. 相似文献
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Loss-of-function mutations in the EGF-CFC gene CFC1 are associated with human left-right laterality defects 总被引:4,自引:0,他引:4
Bamford RN Roessler E Burdine RD Saplakoğlu U dela Cruz J Splitt M Goodship JA Towbin J Bowers P Ferrero GB Marino B Schier AF Shen MM Muenke M Casey B 《Nature genetics》2000,26(3):365-369
All vertebrates display a characteristic asymmetry of internal organs with the cardiac apex, stomach and spleen towards the left, and the liver and gall bladder on the right. Left-right (L-R) axis abnormalities or laterality defects are common in humans (1 in 8,500 live births). Several genes (such as Nodal, Ebaf and Pitx2) have been implicated in L-R organ positioning in model organisms. In humans, relatively few genes have been associated with a small percentage of human situs defects. These include ZIC3 (ref. 5), LEFTB (formerly LEFTY2; ref. 6) and ACVR2B (encoding activin receptor IIB; ref. 7). The EGF-CFC genes, mouse Cfc1 (encoding the Cryptic protein; ref. 9) and zebrafish one-eyed pinhead (oep; refs 10, 11) are essential for the establishment of the L-R axis. EGF-CFC proteins act as co-factors for Nodal-related signals, which have also been implicated in L-R axis development. Here we identify loss-of-function mutations in human CFC1 (encoding the CRYPTIC protein) in patients with heterotaxic phenotypes (randomized organ positioning). The mutant proteins have aberrant cellular localization in transfected cells and are functionally defective in a zebrafish oep-mutant rescue assay. Our findings indicate that the essential role of EGF-CFC genes and Nodal signalling in left-right axis formation is conserved from fish to humans. Moreover, our results support a role for environmental and/or genetic modifiers in determining the ultimate phenotype in humans. 相似文献
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A mechanism for initiating RNA-dependent RNA polymerization 总被引:26,自引:0,他引:26
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D. G. Bamford D. E. Biggs P. Chaplen M. Davis Judith Maconochie 《Cellular and molecular life sciences : CMLS》1972,28(9):1069-1070
Résumé Le M&B 15.944 (éthiodide dep-diméthylaminophényl heptyl cétone thiosémicarbazone) est un curarisant dont la brève durée d'action est comparable à celle de la succinylcholine chez divers espèces y compris le singe. Le méchanisme du blocage neuromusculaire provoqué par le M&B 15.944 est compétitif. 相似文献
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