A 11.5 angstrom single particle reconstruction of GroEL using EMAN

Single-particle analysis has become an increasingly important method for st ructural determination of large macromolecular assemblies. GroEL is an 800 kDa molecular chaperone, which, along with its co-chaperonin GroES, promote s protein folding both in vitro and in the bacterial cell. EMAN is a single -particle analysis software package, which was first publicly distributed i n 2000. We present a three-dimensional reconstruction of native naked GroEL to similar to 11.5 Angstrom performed entirely with EMAN. We demonstrate t hat the single-particle reconstruction, X-ray scattering data and X-ray cry stal structure all agree well at this resolution. These results validate th e specific methods of image restoration, reconstruction and evaluation tech niques implemented in EMAN. It also demonstrates that the single-particle r econstruction technique and X-ray crystallography will yield consistent str ucture factors, even at low resolution, when image restoration is performed correctly. A detailed comparison of the single-particle and X-ray structur es exhibits some small variations in the equatorial domain of the molecule, likely due to the absence of crystal packing forces in the single-particle reconstruction. (C) 2001 Academic Press.