Structural similarities between MutT and the C-terminal Domain of MutY

One of the functions of MutY from Escherchia coli is removal of adenine mispaired with 7,8-dihydro-8-oxoguanine (8-oxoG), a common lesion in oxidatively damaged DNA. MutY is composed of two domains: the larger N-terminal domain (p26) contains the catalytic properties of the enzyme while the C-terminal domain (p13) affects substrate recognition and enzyme turnover. On the basis of sequence analyses, it has been recently suggested that the C-terminal domain is distantly related to MutT, a dNTPase which hydrolyzes 8-oxo-dGTP [Noll et al. (1999) Biochemistry 38, 6374-6379]. We have studied the solution structure of the C-terminal domain of MutY by NMR and find striking similarity with the reported solution structure of MutT. Despite low sequence identity between the two proteins, they have similar secondary structure and topology. The C-terminal domain of MutY is composed of two α-helices and five β-strands. The NOESY data indicate that the protein has two β-sheets. MutT is also a mixed α/β protein with two helices and two β-sheets composed of five strands. The secondary structure elements are similarly arranged in the two proteins.