Cell-Free Synthesis o f Membrane Proteins for X-Ray Crystallography .. J u lia E . F letcher, Federico K a tze n , W ieslaw Kud lic k i, Yen ju C hen,

Introduction Membrane proteins account for nearly a third o f the genes encoded by most fully sequenced

genomes. However, only a handful o f integral membrane protein structures (~ 100) have been solved to high resolution. This disparity is largely a consequence o f several hurdles, which include the requirement for large amounts (~100 mg) o f these proteins for biophysical analysis such as X-ray crystallography, electron microscopy, or nuclear s magnetic resonance. This requirement has generally been difficult to meet by conventional in vivo expression techniques.