Recognition of the Nonpolar Base 4-Methylindole in DNA by the DNA Repair Adenine Glycosylase MutY

The DNA repair adenine glycosylase MutY efficiently recognizes 7-deaza-2‘-deoxyadenosine (Z) and its nonpolar isostere 4-methylindole β-deoxynucleoside (M) opposite 7,8-dihydro-8-oxo-2‘-deoxyguanosine (OG) and G in DNA. Both wild-type and truncated MutY exhibit a 10- to 20-fold higher affinity for a duplex containing OG:M than OG:Z. More efficient recognition of M over Z by MutY may be to due the lack of hydrogen bonding with the OG that facilitates nucleotide flipping during the substrate recognition process.