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Figure 4
Molecular replacement of the RdfS crystal structure. (a) Initial molecular replacement located three RdfS monomers and a patch of unmodelled electron density. (b) Superposition of molecule A of the molecular-replacement solution on molecule C demonstrated a repetitive pattern of head-to-tail interacting monomers, allowing the placement of a fourth monomer. (c) Three orthogonal views of the final molecular-replacement solution, with four molecules in the asymmetric unit, result in a continuous left-handed superhelix with eight molecules per helical turn running through the crystal (pink box, unit cell). (d) The self-rotation function of RdfS indicates eight equally spaced twofold NCS axes (χ = 180°; four nonredundant axes related by a crystallographic twofold axis) and a strong eightfold NCS axis (χ = 45°). (e) Left: the rotational symmetry axes relating a monomer in one molecular superhelix (black) and eight monomers in two other asymmetric units (red, orange, yellow, green and cyan; blue, indigo and violet). The black bar represents the eightfold symmetry axis (χ = 45°) and the coloured bars represent each of the twofold symmetry axes (χ = 180°), as indicated on the self-rotation function. Right: an orthogonal view of the same set of molecules viewed along the eightfold symmetry axis (black).

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ISSN: 2059-7983
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