Two-dimensional structure of plant light-harvesting complex at 37 Å resolution by electron crystallography

The structure of the light-harvesting chlorophyll complex has been determined at 3.7 Å resolution in projection by electron diffraction, electron microscopy and image analysis. Diffraction patterns and high-resolution spotscan images of two-dimensional crystals stabilized with tannin were recorded at low temperature. Phases of structure factors were obtained directly by image processing, after correction of the images for lattice distortions, defocus and beam tilt. Amplitudes were measured by electron diffraction. The projection map shows the detailed structure of the trimeric complex, suggesting the positions of two domains of potential structural and functional homology, of one membrane-spanning α-helix approximately perpendicular to the membrane plane and of several tightly bound lipid molecules