De novo protein structure determination from near-atomic-resolution cryo-EM maps

We present a de novo model-building approach that combines predicted backbone conformations with side-chain fit to density to accurately assign sequence into density maps. This method yielded accurate models for six of nine experimental maps at 3.3- to 4.8-Å resolution and produced a nearly complete model for an unsolved map containing a 660-residue heterodimeric protein. This method should enable rapid and reliable protein structure determination from near-atomic-resolution cryo-electron microscopy (cryo-EM) maps.