Protein Crystallization on Lipid Layers and Structure Determination of the RNA Polymerase II Transcription Initiation Complex

Structure determination of proteins on the order of 104 Da is routinely performed at atomic resolution by x-ray crystallography and NMR. Proteins on the order of 105–106 Da (especially symmetrical protein assemblies) have been solved by x-ray methods, but these larger molecules and molecular arrays are generally studied by electron microscopy. Several small (104 Da) proteins have been determined in near atomic detail by electron methods, but for larger structures, the resolution is typically limited to 10–30 Å.