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On the structures of filamentous bacteriophage Ff (fd, f1, M13)

S K Straus1, W R P Scott, M F Symmons

  • 1Department of Chemistry, University of British Columbia, Vancouver, BC, Canada.

European Biophysics Journal : EBJ
|October 19, 2007
PubMed

Insights

The study reveals discrepancies in the cryo-electron microscopy (cryoEM) model of the filamentous bacteriophage Ff protein coat. Refining the cryoEM model against X-ray data aligns it with previous findings from X-ray fiber diffraction and solid-state NMR.

Area of Science:

  • Molecular biophysics
  • Structural biology
  • Virology

Background:

  • The filamentous bacteriophage (Inovirus) strain Ff (fd, f1, M13) is a key model system in molecular biophysics.
  • Previous structural studies of the Ff protein coat have yielded differing models.
  • A low-resolution cryo-electron microscopy (cryoEM) model has been proposed, distinct from prior X-ray fiber diffraction and solid-state NMR models.

Purpose of the Study:

  • To evaluate the accuracy of the cryoEM model of the Ff protein coat.
  • To compare the cryoEM model with existing data from X-ray fiber diffraction and solid-state NMR.
  • To refine the cryoEM model and reconcile structural discrepancies.

Main Methods:

  • Iterative helical real space reconstruction of cryo-electron micrographs.
  • Analysis of cryoEM model against X-ray fiber diffraction and solid-state NMR data.
  • Refinement of the cryoEM model using X-ray diffraction data.

Main Results:

  • The cryoEM model showed significant disagreement with both solid-state NMR and X-ray fiber diffraction data.
  • The cryoEM model exhibited unusual structural features, including nanometer-scale holes.
  • Refinement of the cryoEM model against X-ray data resulted in a structure closely resembling the established X-ray diffraction and solid-state NMR model.

Conclusions:

  • The initial cryoEM model of the Ff protein coat is inconsistent with established biophysical data.
  • Refinement procedures can reconcile structural models derived from different experimental techniques.
  • Further investigation is needed to understand the origins of discrepancies between cryoEM and X-ray diffraction models.

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