1H, 13C and 15N resonance assignments of the C-terminal domain of MutY: an adenine glycosylase active on G:A mismatches.

Abstract

MutY from Escherichia coli is a DNA mismatch repair enzyme involved in the base excision repair pathway. It is an adenine glycosylase which removes adenine when mispaired with guanine, cytosine or 7,8dihydro-8-oxoguanine (8-oxoG). 8-oxoG is a common DNA oxidative damage lesion and mutant strains of E. coli that lack MutY activity have elevated rates of G:C to T:A tranversions (Nghiem et al., 1988). Trypsin produced an N-terminal domain of residues 1–225, p26, and a C-terminal domain of 226–350, p13 (Manuel et al., 1996). The catalytic activity of the enzyme was found solely in the N-terminal domain. Recent work has determined the crystal structure of the p26 domain; the protein has a helix-hairpin-helix structural motif in common with a number of DNA glycosylases and DNA glycosylase/AP lysases (Guan et al., 1998). The crystal structure suggests that MutY utilizes a nucleotide flipping mechanism, in which the adenine is moved to an extrahelical position within the DNA, into an active site pocket where it is excised. Studies of intact MutY and the N-terminal domain show that the C-terminal domain affects substrate binding and mismatch repair activity. Manuel and Lloyd (1997) found that the largest differences between MutY and p26 in binding of natural substrates involved A:G and in mismatch activity A:C. Recent biochemical data suggest that the C-terminal domain is the principal determinant of 8-oxoG specificity (Noll et al., 1999).