and other MutS2 homologues. This alignment was performed with the ESPript 2.2 program. (TIF) Figure S2 The purity and ATPase activity of TmMutS2. (A) SDS-PAGE analysis of purified TmMutS2 from a 12.5% (w/v) denaturing polyacrylamide gel. The gel was stained with Coomassie blue. The left lane represents size marker proteins. (B) ATP hydrolytic activity of TmMutS2 as determined by PEI- TLC analysis (upper) and the fluorometric real-time method (lower). (C) DLS analysis of TmMutS2 at 37uC (left) and 60uC (right) according to time. (TIF) Figure S3 Endonuclease activity test for other homo- logues of TmMutS2. (A) TmMutS2 (2 mM) and TmMutS2DSmr (2 mM) were reacted with only supercoiled circular DNA (1.5 mM) at 37uC. (B) Plasmid DNA was reacted with 1 mM of TmMutS2-Smr and B3bp-Smr at 37uC. The nick, l, and sc indicate the nicked, linearized, and closely supercoiled open circular DNA forms, respectively. (TIF) Figure S4 DNA-binding affinity of TmMutS2 in the presence of TmMutL. (TIF) Figure S5 Endonuclease activity test for TmMutL. The addition of 1 mM of nucleotides to 2 mM TmMutL. The 0.8% agarose gel indicates that TmMutL has no nicking endonuclease activity and dependence on the nucleotides. The nick and sc indicate the nicked and supercoiled DNA forms, respectively. (TIF) Figure S6 A spontaneous mutation frequency assay using TmmutS2 and TmmutS2DSmr genes. RifR indicates rifampicin-resistance. The frequency of RifR (y-axis)/108 cells is quantitatively analyzed by counting the number of spontaneously mutated colonies. (TIF) Figure S7 The Guinier approximations for the SAXS scattering curves. These plots are for apo-TmMutS2 and its References 1. Lyer RR, Pluciennik A, Burdett V, Modrich PL (2006) DNA Mismatch Repair: Functions and Mechanisms. Chem Rev 106: 302–323. 2. Hopfner KP, Tainer JA (2000) DNA Mismatch Repair: The Hands of a Genome Guardian. Structure 8: R237–R241. 3. Jun SH, Kim TG, Ban C (2006) DNA mismatch repair system. 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Monomeric TmMutS2- Smr was confirmed using a Superdex 75 HR column calibrated with BSA (66 kDa in monomer), a-chymotrypsin (25 kDa), and aprotinin (6.5 kDa). (TIF) Table S1 The fineness parameters of the superimposi- tions. These are for the SAXS models of the TmMutS2 complexes, the TaqS-ATPase structure/TmS2-ATPase model, and the B3bp-Smr structure/TmS2-Smr model. (DOCX) List of specific primers used in this study. List of specific primers used in this study. Table S2 (DOCX) Table S3 (DOCX) Acknowledgments We thank to Prof. Yu-Ryang Pyun (Yonsei Univ., Korea) for providing Thermotoga maritima MSB8 genomic DNA and Kazuki Ito for offering technical supports and helpful discussion at BL45XU beamline with approval of RIKEN SPring-8 Center (Proposal No. 20070154). Author Contributions Conceived and designed the experiments: EJ HJ TGK CB. Performed the experiments: EJ HJ TGK CB. Analyzed the data: TGK CB. Contributed reagents/materials/analysis tools: EJ HJ. 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