a, Structure of the ISWI dimer. One molecule is coloured as in Fig. 1, and the other molecule is coloured grey. b, Chromatin remodelling of the 2D-V638D mutant (black). The activity of the parental 2D mutant was reproduced from Fig. 3e (red). Error bars, s.d. (n = 3). One representative gel was shown in the right panel. c, MALS of the core MtISWI (81–723; blue), 2D mutant (red), and mFL (81–1048; black). Core and mFL MtISWI are predominantly in a monomeric state, with a small fraction of dimer (~6%). The calculated molecular masses of the major peaks of core and mFL MtISWI are ~66 kDa and ~106 kDa, respectively, corresponding to a monomer, whereas the small peaks correspond to the dimer fractions. The 2D mutant shows two peaks with molecular masses of ~68 kDa and ~133 kDa, corresponding to a monomer and a dimer, respectively. d, Superimposition of the core2 domains of the two crystal structures examined in this study. For clarity, only the dimerization interface is shown. One dimer is coloured as in a; the other dimer is coloured yellow and blue. The core2 and NegC domains interact similarly in the two different crystal forms. The Brace helix shows some domain movement relative to NegC. e, ATPase activities of mFL, mFL-2D, and mFL-2D-II/DD in the absence (open bars) and the presence (filled bars) of DNA. Error bars, s.d. (n = 3). f, Representative gels of the overall chromatin remodelling assays of mFL, mFl-2D, and mFl-2D-II/DD. Quantifications of the cut fractions are shown in Fig. 4b.