Nanometric tracking of KIF3AC and engineered homodimers by iSCAT microscopy. (A) Sample traces of KIF3AA (blue), KIF3AC (red), and KIF3CC (green) tracked by iSCAT microscopy shown on the same time and length scales for comparison. Sample traces (B–D) of expanded views of the position along path of travel at 1 mM MgATP for KIF3AA (B), KIF3CC (C), and KIF3AC (D). An asterisk is used to denote instances of pausing for >150 ms in traces of KIF3AA motility. Velocity is reported as the mean ± SD for each motor. N values reflect the number of molecules tracked for iSCAT analysis. Black overlay, Kerssemakers’ algorithm fit (32).