High Resolution Models from Low Resolution Data: Recombination of Fragments for Crystallographic Structure Determination

Abstract

Traditional X-ray crystallographic structure determination observes a low-energy molecular conformation of a target molecule embedded within a periodic macroscopic crystal. Improving technology, accelerated via structural genomics efforts, and increasing access to synchrotrons are two notable factors in the radical acceleration of the process of obtaining crystals and datasets suitable for structure determination. However, any resulting structure provides a limited snapshot or handful of snapshots into the ensemble of relevant molecular conformations. Furthermore, not all molecules of interest can be coaxed into forming a crystal. Here, we demonstrate a method for crystallographic structure determination that observes the conformation for target molecules of interest embedded, piecewise, within homologous protein structures. To demonstrate this new method we have solved the structure of 21 synthetic cytochrome P450 chimeras, as well as two natural cytochrome P450s from Bacillus subtilis. We demonstrate a high level of accuracy for piecewise crystallographic structure determination with unique advantages with respect to traditional crystallography.