title: Structure of a rhombohedral R6 insulin/phenol complex.
abstract: Hexameric insulin has been crystallized from different conditions in a variety of crystalline modifications. In the presence of approximately 1% phenol and at a pH of 8.5, a new rhombohedral form is produced, space group R3, a = 79.92A and c = 40.39A, in which the asymmetric unit consists of a dimer. The structure has been solved and refined, using data between 8.0 and 2.5A resolution, to a residual of 0.157. The two monomers in the asymmetric unit have nearly identical R conformations, that is, residues B1 through B8 are alpha-helical, producing a continuous alpha-helix from B1 through B19. A phenol molecule is hydrogen bonded to the carbonyl oxygen of A6 Cys of each monomer. Small differences in conformation and the final (2Fo-Fc) and difference electron density maps suggest that an additional phenol molecule is coordinated to one of the two zinc ions.
authors.affiliation: Medical Foundation of Buffalo, Inc., New York 14203.
authors.forename: G D
authors.initials: GD
authors.lastname: Smith
authors.forename: G G
authors.initials: GG
authors.lastname: Dodson
mesh_terms: D007328:Insulin / Q000737:chemistry*; D046911:Macromolecular Substances; D019800:Phenol; D010636:Phenols / Q000737:chemistry*; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D007328:Insulin; D046911:Macromolecular Substances; D010636:Phenols; D019800:Phenol