Conformational changes in the catalytic globular domain arrangement of the tetrameric M/R complex as a consequence of ATP binding, hydrolysis and release as revealed by crystallographic studies of thermophilic archaeal and bacterial homologues.
Mre11 components are coloured blue, and Rad50 in red. (A) an ‘M’-shaped extended conformation is observed prior to ATP-binding; the tetramer is joined by dimerization at the Mre11 catalytic domains (ribbon representation of PDB: 3QG5; species: Thermotoga maritima). The two Rad50 subunits attach to each of the Mre11 subunits via the helix–loop–helix region. (B) the two Rad50 molecules associate upon ATP-binding to form the more compact tetrameric complex (ribbon representation of PDB: 3QF7; species: Thermotoga maritima). Note that only the helix–loop–helix regions of Mre11 are shown in this structure. (C) ribbon representation of the closed conformation showing all four subunits of the tetramer and a dsDNA substrate bound to the Rad50 globular domains (PDB: 5F3W; species: Methanocaldococcus jannaschii). Note that the two halves of each Rad50 subunit (encompassing the two Walker boxes) are coloured in red and salmon, respectively, and only the base of the coiled-coil regions are depicted (these extend outwards and join at the zinc-hook hinged region). Figures were created in Pymol.