Two-dimensional crystals of Escherichia coli RNA polymerase holoenzyme on positively charged lipid layers.

Escherichia coli RNA polymerase holoenzyme forms two-dimensional crystals when adsorbed to positively charged lipid layers at the air/water interface. Adsorption of the protein is driven by electrostatic interactions between the positively charged lipid surface and the polymerase molecule, which has a net negative charge. Crystallization is dependent on the adsorption and concentration of RNA polymerase on fluid lipid surfaces. Image analysis of electron micrographs of crystals in negative stain, which diffract to 30 A resolution, shows irregularly shaped protein densities about 100 x 160 A, consistent with the dimensions of single polymerase molecules.