Crystal structure of a repair enzyme of oxidatively damaged DNA, MutM (Fpg), from an extreme thermophile, Thermus thermophilus HB8.
The MutM [formamidopyrimidine DNA glycosylase (Fpg)] protein is a trifunctional DNA base excision repair enzyme that removes a wide range of oxidatively damaged bases (N-glycosylase activity) and cleaves both the 3'- and 5'-phosphodiester bonds of the resulting apurinic/apyrimidinic site (AP lyase activity). The crystal structure of MutM from an extreme thermophile, Thermus thermophilus HB8, was determined at 1.9 A resolution with multiwavelength anomalous diffraction phasing using the intrinsic Zn(2+) ion of the zinc finger. MutM is composed of two distinct and novel domains connected by a flexible hinge. There is a large, electrostatically positive cleft lined by highly conserved residues between the domains. On the basis of the three-dimensional structure and taking account of previous biochemical experiments, we propose a DNA-binding mode and reaction mechanism for MutM. The locations of the putative catalytic residues and the two DNA-binding motifs (the zinc finger and the helix-two-turns-helix motifs) suggest that the oxidized base is flipped out from double-stranded DNA in the binding mode and excised by a catalytic mechanism similar to that of bifunctional base excision repair enzymes.
Department of Biology, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
M
M
Sugahara
T
T
Mikawa
T
T
Kumasaka
M
M
Yamamoto
R
R
Kato
K
K
Fukuyama
Y
Y
Inoue
S
S
Kuramitsu
D000595:Amino Acid Sequence; D001420:Bacteria, Aerobic / Q000201:enzymology; D020134:Catalytic Domain; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D004249:DNA Damage; D018983:DNA Footprinting; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000737:chemistry*; D043382:DNA-Formamidopyrimidine Glycosylase; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000737:chemistry*; D010084:Oxidation-Reduction; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D013379:Substrate Specificity; D013499:Surface Properties; D016963:Thermus thermophilus / Q000201:enzymology; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase