title: Effect of dimethyl sulphoxide on the crystal structure of porcine pepsin.
abstract: The structure of porcine pepsin crystallized in the presence of dimethyl sulphoxide has been analysed by X-ray crystallography to obtain insights into the structural events that occur at the onset of chemical denaturation of proteins. The results show that one dimethyl sulphoxide molecule occupies a site on the surface of pepsin interacting with two of its residues. An increase in the average temperature factor of pepsin in the presence of dimethyl sulphoxide has been observed indicating protein destabilization induced by the denaturant. Significant increase in the temperature factor and weakening of the electron density have been observed for the catalytic water molecule located between the active aspartates. The conformation of pepsin remains unchanged in the crystal structure. However, the enzyme assay and circular dichroism studies indicate that dimethyl sulphoxide causes a slight change in the secondary structure and complete loss of activity of pepsin in solution.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, Karnataka, India.
authors.forename: Muppuru Muni
authors.initials: MM
authors.lastname: Kesavulu
authors.forename: Sundaramoorthy
authors.initials: S
authors.lastname: Ramasubramanian
authors.forename: Kaza
authors.initials: K
authors.lastname: Suguna
mesh_terms: D000818:Animals; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004121:Dimethyl Sulfoxide / Q000494:pharmacology*; D008958:Models, Molecular; D010434:Pepsin A / Q000737:chemistry / Q000187:drug effects*; D013552:Swine
chemical_list: D010434:Pepsin A; D004121:Dimethyl Sulfoxide