2om3: Difference between revisions

Revision as of 19:20, 21 February 2008

High-resolution cryo-EM structure of Tobacco Mosaic Virus

OverviewOverview

The treatment of helical objects as a string of single particles has become an established technique to resolve their three-dimensional (3D) structure using electron cryo-microscopy. It can be applied to a wide range of helical particles such as viruses, microtubules and helical filaments. We have made improvements to this approach using Tobacco Mosaic Virus (TMV) as a test specimen and obtained a map from 210,000 asymmetric units at a resolution better than 5 A. This was made possible by performing a full correction of the contrast transfer function of the microscope. Alignment of helical segments was helped by constraints derived from the helical symmetry of the virus. Furthermore, symmetrization was implemented by multiple inclusions of symmetry-related views in the 3D reconstruction. We used the density map to build an atomic model of TMV. The model was refined using a real-space refinement strategy that accommodates multiple conformers. The atomic model shows significant deviations from the deposited model for the helical form of TMV at the lower-radius region (residues 88 to 109). This region appears more ordered with well-defined secondary structure, compared with the earlier helical structure. The RNA phosphate backbone is sandwiched between two arginine side-chains, stabilizing the interaction between RNA and coat protein. A cluster of two or three carboxylates is buried in a hydrophobic environment isolating it from neighboring subunits. These carboxylates may represent the so-called Caspar carboxylates that form a metastable switch for viral disassembly. Overall, the observed differences suggest that the new model represents a different, more stable state of the virus, compared with the earlier published model.

About this StructureAbout this Structure

2OM3 is a Single protein structure of sequence from Tobacco mosaic virus. Full crystallographic information is available from OCA.

ReferenceReference

High-resolution electron microscopy of helical specimens: a fresh look at tobacco mosaic virus., Sachse C, Chen JZ, Coureux PD, Stroupe ME, Fandrich M, Grigorieff N, J Mol Biol. 2007 Aug 17;371(3):812-35. Epub 2007 Jun 4. PMID:17585939

Page seeded by OCA on Thu Feb 21 18:20:05 2008

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OCA

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 ==Overview==
-The treatment of helical objects as a string of single particles has, become an established technique to resolve their three-dimensional (3D), structure using electron cryo-microscopy. It can be applied to a wide, range of helical particles such as viruses, microtubules and helical, filaments. We have made improvements to this approach using Tobacco Mosaic, Virus (TMV) as a test specimen and obtained a map from 210,000 asymmetric, units at a resolution better than 5 A. This was made possible by, performing a full correction of the contrast transfer function of the, microscope. Alignment of helical segments was helped by constraints, derived from the helical symmetry of the virus. Furthermore, symmetrization was implemented by multiple inclusions of symmetry-related, views in the 3D reconstruction. We used the density map to build an atomic, model of TMV. The model was refined using a real-space refinement strategy, that accommodates multiple conformers. The atomic model shows significant, deviations from the deposited model for the helical form of TMV at the, lower-radius region (residues 88 to 109). This region appears more ordered, with well-defined secondary structure, compared with the earlier helical, structure. The RNA phosphate backbone is sandwiched between two arginine, side-chains, stabilizing the interaction between RNA and coat protein. A, cluster of two or three carboxylates is buried in a hydrophobic, environment isolating it from neighboring subunits. These carboxylates may, represent the so-called Caspar carboxylates that form a metastable switch, for viral disassembly. Overall, the observed differences suggest that the, new model represents a different, more stable state of the virus, compared, with the earlier published model.
+The treatment of helical objects as a string of single particles has become an established technique to resolve their three-dimensional (3D) structure using electron cryo-microscopy. It can be applied to a wide range of helical particles such as viruses, microtubules and helical filaments. We have made improvements to this approach using Tobacco Mosaic Virus (TMV) as a test specimen and obtained a map from 210,000 asymmetric units at a resolution better than 5 A. This was made possible by performing a full correction of the contrast transfer function of the microscope. Alignment of helical segments was helped by constraints derived from the helical symmetry of the virus. Furthermore, symmetrization was implemented by multiple inclusions of symmetry-related views in the 3D reconstruction. We used the density map to build an atomic model of TMV. The model was refined using a real-space refinement strategy that accommodates multiple conformers. The atomic model shows significant deviations from the deposited model for the helical form of TMV at the lower-radius region (residues 88 to 109). This region appears more ordered with well-defined secondary structure, compared with the earlier helical structure. The RNA phosphate backbone is sandwiched between two arginine side-chains, stabilizing the interaction between RNA and coat protein. A cluster of two or three carboxylates is buried in a hydrophobic environment isolating it from neighboring subunits. These carboxylates may represent the so-called Caspar carboxylates that form a metastable switch for viral disassembly. Overall, the observed differences suggest that the new model represents a different, more stable state of the virus, compared with the earlier published model.
 ==About this Structure==
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 [[Category: protein-rna complex]]
-''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed Jan 23 12:40:58 2008''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 18:20:05 2008''