title: Recognition of oxidatively modified bases within the biotin-binding site of avidin.
abstract: Oxidative damage of DNA results in the formation of many products, including 8-oxodeoxyguanosine, which has been used as a marker to quantify DNA damage. Earlier studies have demonstrated that avidin, a protein prevalent in egg-white and which has high affinity for the vitamin biotin, binds to 8-oxodeoxyguanosine and related bases. In this study, we have determined crystal structures of avidin in complex with 8-oxodeoxyguanosine and 8-oxodeoxyadenosine. In each case, the base is observed to bind within the biotin-binding site of avidin. However, the mode of association between the bases and the protein varies and, unlike in the avidin:biotin complex, complete ordering of the protein in this region does not accompany binding. Fluorescence studies indicate that in solution the individual bases, and a range of oligonucleotides, bind to avidin with micromolar affinity. Only one of the modes of binding observed is consistent with recognition of oxidised purines when incorporated within a DNA oligomer, and from this structure a model is proposed for the selective binding of avidin to DNA containing oxidatively damaged deoxyguanosine. These studies illustrate the molecular basis by which avidin might act as a marker of DNA damage, although the low levels of binding observed are inconsistent with the recognition of oxidised purines forming a major physiological role for avidin.
authors.affiliation: Department of Biochemistry, University of Bristol, Bristol BS8 1TD, UK.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Conners
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hooley
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Clarke
authors.forename: Siân
authors.initials: S
authors.lastname: Thomas
authors.forename: R Leo
authors.initials: RL
authors.lastname: Brady
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D001360:Avidin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D001710:Biotin / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D003839:Deoxyadenosines / Q000737:chemistry* / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D010084:Oxidation-Reduction; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D003839:Deoxyadenosines; D001360:Avidin; C078251:2'-deoxy-7,8-dihydro-8-oxoadenosine; D001710:Biotin; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA; D003849:Deoxyguanosine