Molecular determinants for MT association of Drp1. (A–F) GFP-Drp1 mutants diagrammed in A were substituted into HeLa cells and analyzed for colocalization with MTs (C, α-tubulin immunofluorescence), effects on mitochondrial shape (D, cytochrome oxidase II), and mobility by FRAP (E and F). Shown are epifluorescence images of GFP-Drp1 localization (B), MT colocalization scores (C), mitochondrial morphometry (D; means ± SEM [up]/SD [down] of 124–158 cells), as well as fluorescence recovery curves (E) and their 50% recovery time constants (F; means ± SEM [up]/SD [down] of 7–14 cells) from representative experiments. ○, P < 0.05; Ø, P < 0.001; ⊗, P < 10⁻⁹; *, P < 10⁻¹¹ compared with Drp1-101 wild type.