title: Reconstitution of apo-porphobilinogen deaminase: structural changes induced by cofactor binding.
abstract: Expression of porphobilinogen deaminase in a hemB- strain of E. coli has permitted the isolation of the apoenzyme, i.e. deaminase lacking the porphobilinogen-derived dipyrromethane cofactor. Incubation of purified apoenzyme with porphobilinogen resulted in reconstitution of the covalently attached dipyrromethane cofactor, indicating no additional cofactors or enzymes are required for biosynthesis of holoenzyme. Electrophoretic and 13C-NMR spectroscopic analyses demonstrate that the apoenzyme exists in a conformationally unstable form which is converted to a highly stable tertiary structure on covalent attachment of the dipyrromethane cofactor.
authors.affiliation: Department of Chemistry, Texas A&M University, College Station 77843.
authors.forename: A I
authors.initials: AI
authors.lastname: Scott
authors.forename: K R
authors.initials: KR
authors.lastname: Clemens
authors.forename: N J
authors.initials: NJ
authors.lastname: Stolowich
authors.forename: P J
authors.initials: PJ
authors.lastname: Santander
authors.forename: M D
authors.initials: MD
authors.lastname: Gonzalez
authors.forename: C A
authors.initials: CA
authors.lastname: Roessner
mesh_terms: D000642:Ammonia-Lyases / Q000378:metabolism*; D001051:Apoenzymes / Q000378:metabolism; D001059:Apoproteins / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D011163:Hydroxymethylbilane Synthase / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008970:Molecular Weight; D011162:Porphobilinogen / Q000378:metabolism*
chemical_list: D001051:Apoenzymes; D001059:Apoproteins; D011162:Porphobilinogen; D011163:Hydroxymethylbilane Synthase; D000642:Ammonia-Lyases