K129E reduces the affinity of survivin for borealin. (A) HeLa cells expressing WT or K129E (green), depleted of endogenous survivin were fixed with formaldehyde and probed to localise borealin (red) at the centromeres of prometaphase cells or (B) at the anaphase spindle. (C) Immunoblot of borealin co-immunoprecipitated with anti-GFP antibodies from lysates prepared from cells ectopically expressing GFP, WT or K129E. (D-F) 3D ribbon models of survivin (grey) bound to the NH2 terminus of borealin (black) constructed from structure 2RAW using UCSF Chimera . K129 and its side chain are highlighted in red. (E, F) Magnified and rotated models of the C-terminus of survivin bound to borealin from (D), with the side chain of D29 of borealin (black), and (F) an upstream glutamic acid (E125svn) indicated in blue mesh to demonstrate how this charge change could affect the proximity of K129svn (red mesh) and D29bor (black mesh).