title: Multiple active conformers of mouse ornithine decarboxylase.
abstract: Purified recombinant mouse ornithine decarboxylase (ODC) was denatured with urea or with guanidinium chloride. Enzymic activity was efficiently recovered upon dilution of the denaturing agent. ODC renatured after urea treatment was further characterized. Kinetics of decarboxylation of the natural substrate ornithine or of the suicide substrate alpha-difluoromethylornithine (DFMO) were not significantly changed by denaturation/renaturation. Surprisingly, the renatured enzyme was not stably labelled with radioactive DFMO, in contrast with the native enzyme not subjected to denaturation. Native and renatured ODC did not differ in their c.d. spectra, but the former contained four reactive cysteine residues and the latter seven. These data indicate that a conformational change results from denaturation/renaturation that does not alter decarboxylation of substrates, but does change the accessibility or stability of the cysteine-360 residue modified by decarboxylated DFMO.
authors.affiliation: Department of Microbiology and Immunology, University of California San Francisco 94143.
authors.forename: S E
authors.initials: SE
authors.lastname: Tsirka
authors.forename: C W
authors.initials: CW
authors.lastname: Turck
authors.forename: P
authors.initials: P
authors.lastname: Coffino
mesh_terms: D000818:Animals; D001665:Binding Sites; D003653:Decarboxylation; D000518:Eflornithine / Q000737:chemistry / Q000378:metabolism; D019791:Guanidine; D006146:Guanidines / Q000737:chemistry; D051379:Mice; D009154:Mutation; D009955:Ornithine Decarboxylase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D011489:Protein Denaturation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014508:Urea / Q000737:chemistry
chemical_list: D006146:Guanidines; D011994:Recombinant Proteins; D014508:Urea; D009955:Ornithine Decarboxylase; D019791:Guanidine; D000518:Eflornithine