WxxxE-dependent protection of microtubule from nocodazole-induced depolymerisation by BtpB. HeLa cells were transiently transfected with plasmids encoding GFP-BtpB (A-B), GFP-Btp W263S (C, D), or GFP-BtpB E267A (E, F). Sixteen hours after transfection, cells were left untreated (A, C, E), or treated (B, D, F) with 1 μg/ml nocodazole for 30 min, fixed and stained with mouse anti β-tubulin antibody, followed by detection with anti-mouse Texas Red. (A-F) Individual green and red fluorescence and overlay images of HeLa cells. Scale bar, 25 μm. Data are representative of 3 or more independent experiments.