Three-dimensional Reconstruction of the Surface Protein of Pyrodictium brockii: Comparing Two Image Processing Strategies

The three-dimensional structure of the surface layer protein of the hyperthermophilic archaebacterium Pyrodictium brockii was determined by electron crystallographic techniques to a resolution of approximately 1.6 nm. Two image processing strategies—correlation averaging and lattice unbending—were explored with regard to their potential to compensate for lattice distortions. Reconstructions performed via these two routes did not show any significant difference although the unbending approach might be expected to give superior results since, in principle, it incorporates a correction for unit cell displacement, rotation, and deformation while conventional correlation averaging compensates for displacements only. The discussion furthermore addresses some hitherto ignored problems associated with the correction of lattice disorder at higher tilts