title: Crystal structure of alpha-momorcharin in 80% acetonitrile--water mixture.
abstract: Crystals of alpha-momorcharin (MMC) were cross-linked and soaked in an 80% acetonitrile--water mixture and X-ray data were collected to 2.2 A resolution. MMC is a ribosome-inactivating protein with a sugar chain on Asn-227. In previous studies, the whole conformation of the sugar chain could not be obtained in the aqueous system. Here the structure of MMC in a low water system is shown to be similar to the native one, but the sugar chain on Asn-227 is defined by the electron density map. Several oxygen atoms of the oligosaccharide formed intramolecular hydrogen bonds to the protein moiety. The conformation of the residues in the active center is similar to that in the aqueous system. Our results show conformational alteration of the tetrasaccharide of MMC in organic media. They indicate that the oligosaccharides are more rigid in organic solvents. X-ray determination in organic media may be used to solve some structures of oligosaccharides linked to glycoproteins.
authors.affiliation: Department of Chemistry, Peking University, Beijing 100871, PR China.
authors.forename: G
authors.initials: G
authors.lastname: Zhu
authors.forename: Q
authors.initials: Q
authors.lastname: Huang
authors.forename: M
authors.initials: M
authors.lastname: Qian
authors.forename: Y
authors.initials: Y
authors.lastname: Tang
mesh_terms: D000097:Acetonitriles; D000255:Adenosine Triphosphate / Q000737:chemistry; D018360:Crystallography, X-Ray; D005976:Glutaral / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D010940:Plant Proteins / Q000737:chemistry*; D012269:Ribosomal Proteins; D054788:Ribosome Inactivating Proteins; D012997:Solvents; D013237:Stereoisomerism; D014867:Water
chemical_list: D000097:Acetonitriles; D010940:Plant Proteins; D012269:Ribosomal Proteins; D012997:Solvents; D014867:Water; C039582:MMC protein, Momordica charantia; D000255:Adenosine Triphosphate; D054788:Ribosome Inactivating Proteins; D005976:Glutaral; C032159:acetonitrile