Rapid isolation of bacterial photosynthetic reaction centers with an engineered poly-histidine tag

A very rapid method for isolating bacterial photosynthetic reaction centers (RCs) of high purity and yield is described. A poly-histidine tag is engineered at the C-terminus of the RC M-subunit, allowing recovery of pure RCs in less than 4 h with a commercially available Ni2+ resin. The phenotype of the protein including absorption spectra and electron transfer kinetics are virtually identical to wild-type RCs. This method should facilitate studies of RCs by dramatically decreasing sample preparation time and eliminating the use of expensive equipment.