Crystal structure and nanoanatomy of the E. coli RecA protein

Abstract

The E. coli RecA homolog has been previously crystallized in four conformations (Xing & Bell 2004). We have determined the crystal structure of the E. coli RecA protein to 2.5Å in novel magnesium solution conditions. To facilitate a clear discussion of structure, we introduce a nomenclature based upon our description of RecA protein “nanoanatomy”. Namely, the anterior face of the RecA monomer is defined as the side pointing toward the filament interior. We also propose names for the “bioinformatic elements” of the RecA protein as visualized by ProfileGrids. Previous E. coli RecA structures had disordered L1/L2 loops and the last 25 residues of the C‐terminus. By contrast, low resolution structures of these regions was revealed by the Mycobacterial RecA homologs (Vijayan & co‐workers 2000‐2007). We propose a model for these parts of the E. coli RecA protein. First, the L2 loop follows the filament right‐handed helical path. Second, within the monomer posterior groove we observe the C‐terminus. In general, these E. coli RecA loop conformations are opposite from seen in the Mycobacterial RecA structures. [AIR supported by a NIH Diversity Supplement and a UC President's Postdoctoral Fellowship.]