title: Small-angle X-ray scattering analysis reveals the ATP-bound monomeric state of the ATPase domain from the homodimeric MutL endonuclease, a GHKL phosphotransferase superfamily protein.
abstract: DNA mismatch repair is an excision system that removes mismatched bases chiefly generated by replication errors. In this system, MutL endonucleases direct the excision reaction to the error-containing strand of the duplex by specifically incising the newly synthesized strand. Both bacterial homodimeric and eukaryotic heterodimeric MutL proteins belong to the GHKL ATPase/kinase superfamily that comprises the N-terminal ATPase and C-terminal dimerization regions. Generally, the GHKL proteins show large ATPase cycle-dependent conformational changes, including dimerization-coupled ATP binding of the N-terminal domain. Interestingly, the ATPase domain of human PMS2, a subunit of the MutL heterodimer, binds ATP without dimerization. The monomeric ATP-bound state of the domain has been thought to be characteristic of heterodimeric GHKL proteins. In this study, we characterized the ATP-bound state of the ATPase domain from the Aquifex aeolicus MutL endonuclease, which is a homodimeric GHKL protein unlike the eukaryotic MutL. Gel filtration, dynamic light scattering, and small-angle X-ray scattering analyses clearly showed that the domain binds ATP in a monomeric form despite its homodimeric nature. This indicates that the uncoupling of dimerization and ATP binding is a common feature among bacterial and eukaryotic MutL endonucleases, which we suggest is closely related to the molecular mechanisms underlying mismatch repair.
authors: RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo-cho, Sayo-Gun, Hyogo, 679-5148, Japan.
authors: Hitoshi
authors: H
authors: Iino
authors: Takaaki
authors: T
authors: Hikima
authors: Yuya
authors: Y
authors: Nishida
authors: Masaki
authors: M
authors: Yamamoto
authors: Seiki
authors: S
authors: Kuramitsu
authors: Kenji
authors: K
authors: Fukui
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000595:Amino Acid Sequence; D001419:Bacteria / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D008969:Molecular Sequence Data; D011485:Protein Binding; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D001426:Bacterial Proteins; D021122:Protein Subunits; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases