THE PROJECTION STRUCTURE OF MICROSOMAL GLUTATHIONE TRANSFERASE

Through the use of electron crystallography, it has been possible to o btain high resolution structural information regarding a mammalian pro tein that spans the lipid bilayer. Two-dimensional crystal of the deto xification enzyme microsomal glutathione transferase were induced by s low detergent removal from a mixture containing low amounts of phospho lipid. Images of specimens stabilized in tannin were collected using e lectron cryomicroscopy. The projection structure at 4 Angstrom shows t ightly packed trimers of the protein, Each of them contains an inner c ore of six parallel alpha-helices delineating a central low density re gion. The helical bundle is partly surrrounded by elongated domains.