title: Site-directed mutagenesis and characterization of uracil-DNA glycosylase inhibitor protein. Role of specific carboxylic amino acids in complex formation with Escherichia coli uracil-DNA glycosylase.
abstract: Bacteriophage PBS2 uracil-DNA glycosylase inhibitor (Ugi) protein inactivates uracil-DNA glycosylase (Ung) by acting as a DNA mimic to bind Ung in an irreversible complex. Seven mutant Ugi proteins (E20I, E27A, E28L, E30L, E31L, D61G, and E78V) were created to assess the role of various negatively charged residues in the binding mechanism. Each mutant Ugi protein was purified and characterized with respect to inhibitor activity and Ung binding properties relative to the wild type Ugi. Analysis of the Ugi protein solution structures by nuclear magnetic resonance indicated that the mutant Ugi proteins were folded into the same general conformation as wild type Ugi. All seven of the Ugi proteins were capable of forming a Ung.Ugi complex but varied considerably in their individual ability to inhibit Ung activity. Like the wild type Ugi, five of the mutants formed an irreversible complex with Ung; however, the binding of Ugi E20I and E28L to Ung was shown to be reversible. The tertiary structure of [13C,15N]Ugi in complex with Ung was determined by solution state multi-dimensional nuclear magnetic resonance and compared with the unbound Ugi structure. Structural and functional analysis of these proteins have elucidated the two-step mechanism involved in Ung.Ugi association and irreversible complex formation.
authors.affiliation: Department of Agricultural Chemistry, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Lundquist
authors.forename: R D
authors.initials: RD
authors.lastname: Beger
authors.forename: S E
authors.initials: SE
authors.lastname: Bennett
authors.forename: P H
authors.initials: PH
authors.lastname: Bolton
authors.forename: D W
authors.initials: DW
authors.lastname: Mosbaugh
mesh_terms: D017103:Bacillus Phages / Q000201:enzymology*; D001667:Binding, Competitive; D045647:DNA Glycosylases; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005814:Genes, Viral; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D017354:Point Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D051981:Uracil-DNA Glycosidase; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism; D015678:Viral Structural Proteins / Q000235:genetics
chemical_list: D014764:Viral Proteins; D015678:Viral Structural Proteins; C027619:uracil-DNA glycosylase inhibitor protein, B. subtilis bacteriophage; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D051981:Uracil-DNA Glycosidase