Automated protein model building combined with iterative structure refinement

In protein crystallography, much time and effort are often required to trac e an initial model from an interpretable electron density map and to refine it until it best agrees with the crystallographic data. Here, we present a method to build and refine a protein model automatically and without user intervention, starting from diffraction data extending to resolution higher than 2.3 Angstrom and reasonable estimates of crystallographic phases. The method is based on an iterative procedure that describes the electron dens ity map as a set of unconnected atoms and then searches for protein-like pa tterns. Automatic pattern recognition (model building) combined with refine ment, allows a structural model to be obtained reliably within a few CPU ho urs. We demonstrate the power of the method with examples of a few recently solved structures.