title: Characterization of an Escherichia coli mutant MutY with a cysteine to alanine mutation at the iron-sulfur cluster domain.
abstract: Escherichia coli MutY is an adenine and a weak guanine DNA glycosylase involved in reducing mutagenic effects of 7,8-dihydro-8-oxoguanine (8-oxoG). The [4Fe-4S] cluster of MutY is ligated by four conserved cysteine residues and has been shown to be important in substrate recognition. Here, we show that the C199A mutant MutY is very insoluble and can be denatured and renatured to regain activity only if iron and sulfur are present in the renaturation steps. The solubility of C199A-MutY can be improved substantially as a fusion protein containing streptococcal protein G (GB1 domain) at its N-terminus. Here, we describe the first biochemical characterization of the purified GB1-C199A-MutY protein which contains a [3Fe-4S] cluster. The apparent dissociation constant (K(d)) values of GB1-C199A-MutY with both A/G and A/8-oxoG mismatches are slightly higher than that of the wild-type protein. The DNA glycosylase activity of GB1-C199A-MutY is comparable to that of the wild-type enzyme. Interestingly, the major difference between the C199A-MutY and wild-type proteins is their trapping activities (formation of Schiff base intermediates). The GB1-C199A-MutY mutant has a weaker trapping activity than the wild-type enzyme. Importantly, highly expressed GB1-C199A-MutY and untagged C199A-MutY can complement mutY mutants; however, GB1-C199A-MutY and untagged C199A-MutY cannot complement mutY mutants in vivo when both proteins are poorly expressed. Therefore, an intact [4Fe-4S] cluster domain is critical for MutY stability and activity.
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, Maryland 21201, USA. aluchang@umaryland.edu
authors.forename: A-Lien
authors.initials: AL
authors.lastname: Lu
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Wright
mesh_terms: D000409:Alanine / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003545:Cysteine / Q000235:genetics*; D045647:DNA Glycosylases; D017931:DNA Primers / Q000737:chemistry; D004260:DNA Repair / Q000235:genetics; D004269:DNA, Bacterial / Q000378:metabolism; D004789:Enzyme Activation / Q000235:genetics; D004795:Enzyme Stability / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D007506:Iron-Sulfur Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D009699:N-Glycosyl Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011485:Protein Binding / Q000235:genetics; D011489:Protein Denaturation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; C034284:IgG Fc-binding protein, Streptococcus; D007506:Iron-Sulfur Proteins; D011993:Recombinant Fusion Proteins; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C061738:mutY adenine glycosylase; D003545:Cysteine; D000409:Alanine