title: Catalytic activity of bovine seminal ribonuclease is essential for its immunosuppressive and other biological activities.
abstract: Bovine seminal ribonuclease (BS-RNase) is a homologue of RNase A with special biological properties, including potent immunosuppressive activity. A mutant BS-RNase was created in which His-119, the active-site residue that acts as a general acid during catalysis, was changed to an aspartic acid. H119D BS-RNase formed a dimer with quaternary structure similar to that of the wild-type enzyme but with values of kcat. and kcat./Km for the cleavage of UpA [uridylyl(3'-->5')adenosine] that were 4 x 10(3)-fold lower. The mutant protein also demonstrated dramatically decreased immunosuppressive, anti-tumour, aspermatogenic, and embryotoxic activities. The catalytic activity of BS-RNase is therefore necessary for its special biological properties.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison 53706-1569, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Kim
authors.forename: J
authors.initials: J
authors.lastname: Soucek
authors.forename: J
authors.initials: J
authors.lastname: Matousek
authors.forename: R T
authors.initials: RT
authors.lastname: Raines
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents; D002417:Cattle; D004622:Embryo, Mammalian / Q000187:drug effects; D007166:Immunosuppressive Agents; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D012260:Ribonucleases / Q000378:metabolism* / Q000633:toxicity; D012661:Semen / Q000201:enzymology*; D013091:Spermatogenesis / Q000187:drug effects; D013329:Structure-Activity Relationship
chemical_list: D000970:Antineoplastic Agents; D007166:Immunosuppressive Agents; D012260:Ribonucleases