title: Co-crystals of gramicidin A and phospholipid. A system for studying the structure of a transmembrane channel.
abstract: Single crystals of a complex of gramicidin A, a transmembrane channel-forming polypeptide, and dipalmitoyl phosphatidylcholine, a phospholipid, have been prepared and characterized by X-ray diffraction. They belong to space group P222(1), with unit cell dimensions a = 26.8 A, b = 27.5 A, c = 32.8 A. The asymmetric unit appears to be a complex of one gramicidin monomer and two phospholipid molecules. The unit cell dimensions, space group, and chemical composition are compatible with lipids packing in a bilayer-like motif, and an end-to-end association of gramicidin monomers to form a functional dimeric unit. The crystals diffract to 2 A and are suitable for structural studies by single-crystal X-ray analysis. This represents the first example of a well-ordered crystalline channel complexed with lipids, and solution of its structure may give insight into mechanisms of ion transport across membranes.
authors.affiliation: Department of Chemistry, Rensselaer Polytechnic Institute, Troy, NY 12180.
authors.forename: B A
authors.initials: BA
authors.lastname: Wallace
authors.forename: R W
authors.initials: RW
authors.lastname: Janes
mesh_terms: D006096:Gramicidin / Q000737:chemistry*; D007473:Ion Channels / Q000737:chemistry*; D008958:Models, Molecular; D010743:Phospholipids / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D007473:Ion Channels; D010743:Phospholipids; D006096:Gramicidin