The crystal structure of glutathione

Abstract

The tripeptide glutathione (y-~.-glutamyl-~-cysteinyl-glycine, Cx0H~;NaO~S) crystallizes in the orthorhombie system with space group P2~2~2~ and unit-cell dimensions a = 28-054-0-02, b-8.802+0"002, c = 5"630___0.002 A. The positions of the sulphur atoms in the unit cell were determined from the Harker sections of the three-dimensional Patterson ftmction. The structure was finally determined from a c-axis Fourier projection pattern based on terms with signs derived by the method of Cochran & Douglas, used in conjunction with a three-dimensional electron-density distribution based on terms with phase angles given by the sulphur atoms only. The structure was refined by two-and three-dimensional Fourier s:~ntheses. The molecule contains no unusual bond lengths or angles and adopts a curled configuration with the planes of the glycine carboxyl group and the amino-carboxyl group both parallel to the c-axis, and the planar peptide linkages inclined at 94-4 ° to one another. The sulphur atoms form zigzag chains about alternate screw diad axes parallel to c, the S-S distance being 4.41 A. The structure is held together by a three-dimensional network of hydrogen bonds, but there are no internal hydrogen bonds in the molecule.