Browsing by Subject "IHRSR"

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    Post-translational cleavage of recombinantly expressed nitrilase from Rhodococcus rhodochrous J1 yields a stable, active helical form
    (Wiley, 2007) Thuku, R Ndoria; Weber, Brandon W; Varsani, Arvind; Sewell, B. Trevor
    Nitrilases convert nitriles to the corresponding carboxylic acids and ammonia. The nitrilase from Rhodococcus rhodochrous J1 is known to be inactive as a dimer but to become active on oligomerization. The recombinant enzyme undergoes post-translational cleavage at approximately residue 327, resulting in the formation of active, helical homo-oligomers. Determining the 3D structure of these helices using electron microscopy, followed by fitting the stain envelope with a model based on homology with other members of the nitrilase superfamily, enables the interacting surfaces to be identified. This also suggests that the reason for formation of the helices is related to the removal of steric hindrance arising from the 39 C-terminal amino acids from the wild-type protein. The helical form can be generated by expressing only residues 1-327.
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    Three-dimensional reconstruction of biological macromolecular complexes from in-lens scanning electron micrographs
    (Wiley, 2009) Woodward, J D; Wepf, R; Sewell, B T
    Two helical samples: F-actin and the bacteriophage T4 tail sheath were reconstructed in three dimensions from contrast enhanced (rotational shadowing and negatively stained) in-lens cryo-field emission scanning electron micrographs, using the iterative real-space helical reconstruction method. The F-actin--and bacteriophage T4 reconstructions compare favourably to an atomic model refined against fibre diffraction data and a cryo-electron microscopy reconstruction, respectively. These results show that single-particle methods, developed for macromolecules imaged in the transmission electron microscope can be applied to cryo-field emission scanning electron micrographs data with appropriate symmetry.