title: Human MSH2 (hMSH2) protein controls ATP processing by hMSH2-hMSH6.
abstract: The mechanics of hMSH2-hMSH6 ATP binding and hydrolysis are critical to several proposed mechanisms for mismatch repair (MMR), which in turn rely on the detailed coordination of ATP processing between the individual hMSH2 and hMSH6 subunits. Here we show that hMSH2-hMSH6 is strictly controlled by hMSH2 and magnesium in a complex with ADP (hMSH2(magnesium-ADP)-hMSH6). Destabilization of magnesium results in ADP release from hMSH2 that allows high affinity ATP binding by hMSH6, which then enhances ATP binding by hMSH2. Both subunits must be ATP-bound to efficiently form a stable hMSH2-hMSH6 hydrolysis-independent sliding clamp required for MMR. In the presence of magnesium, the ATP-bound sliding clamps remain on the DNA for ∼8 min. These results suggest a precise stepwise kinetic mechanism for hMSH2-hMSH6 functions that appears to mimic G protein switches, severely constrains models for MMR, and may partially explain the MSH2 allele frequency in Lynch syndrome or hereditary nonpolyposis colorectal cancer.
authors.affiliation: University of Connecticut Health Center, Farmington, Connecticut 06030-3101, USA. cheinen@uchc.edu
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Heinen
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Cyr
authors.forename: Christopher
authors.initials: C
authors.lastname: Cook
authors.forename: Nidhi
authors.initials: N
authors.lastname: Punja
authors.forename: Miho
authors.initials: M
authors.lastname: Sakato
authors.forename: Robert A
authors.initials: RA
authors.lastname: Forties
authors.forename: Juana Martin
authors.initials: JM
authors.lastname: Lopez
authors.forename: Manju M
authors.initials: MM
authors.lastname: Hingorani
authors.forename: Richard
authors.initials: R
authors.lastname: Fishel
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000201:enzymology / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D051718:MutS Homolog 2 Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; D009097:Multienzyme Complexes; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein