title: The hydrolytic water molecule in trypsin, revealed by time-resolved Laue crystallography.
abstract: Crystals of bovine trypsin were acylated at the reactive residue, serine 195, to form the transiently stable p-guanidinobenzoate. Hydrolysis of this species was triggered in the crystals by a jump in pH. The hydrolysis was monitored by three-dimensional Laue crystallography, resulting in three x-ray diffraction structures, all from the same crystal and each representing approximately 5 seconds of x-ray exposure. The structures were analyzed at a nominal resolution of 1.8 angstroms and were of sufficient quality to reproduce subtle features in the electron-density maps for each of the structures. Comparison of the structures before and after the pH jump reveals that a water molecule has positioned itself to attack the acyl group in the initial step of the hydrolysis of this transient intermediate.
authors.affiliation: Biology Department, Argonne National Laboratory, IL 60439.
authors.forename: P T
authors.initials: PT
authors.lastname: Singer
authors.forename: A
authors.initials: A
authors.lastname: Smalås
authors.forename: R P
authors.initials: RP
authors.lastname: Carty
authors.forename: W F
authors.initials: WF
authors.lastname: Mangel
authors.forename: R M
authors.initials: RM
authors.lastname: Sweet
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003461:Crystallography / Q000379:methods; D007202:Indicators and Reagents; D008958:Models, Molecular; D011487:Protein Conformation; D012694:Serine; D014357:Trypsin / Q000737:chemistry*; D014867:Water
chemical_list: D007202:Indicators and Reagents; D014867:Water; D012694:Serine; D014357:Trypsin