Analytical ultracentrifugation of SgrAI with secondary site containing DNA (HEX-18-2). A. Sedimentation equilibrium experiment with 7 µM SgrAI and 3.6 µM HEX-18-2 in 20 mM Tris-OAc (pH 8.0), 50 mM KOAc, 1 mM DTT, 10 mM Ca(OAc)2 at 4°C at 13,500 rpm. Upper panel: Data shown as filled circles, the line corresponds to a fit of a single species with molecular weight of 90.7 kDa. Lower panel: residuals between fit and data. B. Sedimentation velocity c(s) distribution of 6 µM SgrAI and 3 µM HEX-18-2 in 20 mM Tris-OAc (pH 8.0), 50 mM KOAc, 1 mM DTT, 10 mM Ca(OAc)2 at 4°C.