Expression of KBPΔ250–281 leads to aggregation of mitochondria. A, 1 μg of GST-KIF1Bα fusion protein was incubated with equal amounts of lysates from either KBP or KBPΔ250–281 expressing 293 cells. As a control, GST-Grb2 fusion protein was used. The proteins were separated by SDS-PAGE, transferred to nitrocellulose and immunoblotted with GST-KBP antiserum (left panel). To confirm expression of KBP and the KBP deletion mutant, an equal amount of each lysate was loaded on the gel and analysed with KBP antiserum (right panel). Molecular mass markers are shown in kDa, and an arrow indicates the position of KBP. B, NIH3T3 cells transiently overexpressing the KBPΔ250–281 mutant protein were costained with KBP antibody (upper picture) and MitoTracker (lower picture). Trf, transfection; bar, 10 μm.