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- Koeck, Philip J. B., et al.
(författare)
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3D-correlation-averaging for membrane-protein-crystals
- 2008
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Ingår i: EMC 2008 14th European Microscopy Congress. - Berlin, Heidelberg : Springer Berlin Heidelberg. ; , s. 55-56
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Konferensbidrag (refereegranskat)abstract
- Few 2-dimensional protein crystals can be used to determine high-resolution structures, whereas most electron crystallography projects remain at a resolution around 10 Ångström. This might be partly due to lack of flatness of many two-dimensional crystals [1]. We have investigated this problem and suggest single particle projection matching (3D-correlation averaging) of locally averaged unit cells to improve the quality of three-dimensional maps. Theoretical considerations and tests on simulated data demonstrate the feasibility of this refinement method [2].
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| 2. |
- Koeck, Philip J. B., et al.
(författare)
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Single particle refinement in electron crystallography : A pilot study
- 2007
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Ingår i: Journal of Structural Biology. - : Elsevier BV. - 1047-8477 .- 1095-8657. ; 160:3, s. 344-352
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Tidskriftsartikel (refereegranskat)abstract
- Electron crystallography can be used to determine the structures of membrane proteins at near-atomic resolution in some cases. However, most electron crystallography projects remain at a resolution around 10 Å. This might be partly due to lack of flatness of many two-dimensional crystals. We have investigated this problem and suggest single particle processing of locally averaged unit cells to improve the quality and possibly the resolution of three-dimensional maps. Applying this method to the secondary transporter melibiose permease we have calculated a three-dimensional map that is clearer and easier to interpret than the map derived using purely electron-crystallographic methods.
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| 5. |
- Purhonen, P., et al.
(författare)
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Association of renal Na,K-ATPase alpha-subunit with the beta- and gamma-subunits based on cryoelectron microscopy
- 2006
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Ingår i: Journal of Membrane Biology. - : Springer Science and Business Media LLC. - 0022-2631 .- 1432-1424. ; 214:3, s. 139-146
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Tidskriftsartikel (refereegranskat)abstract
- Na,K-ATPase transports Na+ and K+ across cell membranes and consists of alpha- and beta-subunits. Na,K-ATPase also associates with small FXYD proteins that regulate the activity of the pump. We have used cryoelectron microscopy of two-dimensional crystals including data to 8 A resolution to determine the three-dimensional (3-D) structure of renal Na,K-ATPase containing FXYD2, the gamma-subunit. A homology model for the a- subunit was calculated from a Ca2+-ATPase structure and used to locate the additional beta- and gamma-subunits present in the 3-D map of Na,K-ATPase. Based on the 3-D map, the beta- subunit is located close to transmembrane helices M8 and M10 and the gamma-subunit is adjacent to helices M2 and M9 of the alpha-subunit.
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| 10. |
- Purhonen, P, et al.
(författare)
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Three-dimensional Structure of the Sugar Symporter Melibiose Permease from Cryo-electron Microscopy
- 2005
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Ingår i: Journal of Structural Biology. - : Elsevier BV. - 1047-8477 .- 1095-8657. ; 152, s. 76-83
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Tidskriftsartikel (refereegranskat)abstract
- Melibiose permease (MelB) of Escherichia coli is a secondary transporter that couples the uptake of melibiose and various other galactosides to symport of cations that can be Na+, Li+ or H+. MelB belongs to the glycoside-pentoside-hexuronide: cation symporter family of porters and is suggested to have 12 transmembrane helices. We have determined the three-dimensional structure of MelB at 10 angstrom resolution in the membrane plane with cryo-electron microscopy from two-dimensional crystals. The three-dimensional map shows a heart-shaped molecule composed of two domains with a large central cavity between them. The structure is constricted at one side of the membrane while it is open to the other. The overall molecular shape resembles those of lactose permease and glycerol-3-phosphate transporter. However, organization of helices in MOB seems less symmetrical than in these two members of the major facilitator superfamily.
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