Figure 1. Motility Properties of Kinesins with Extended Neck Linkers(A) Various lengths of polyproline and glycine-serine repeats, preceded by two lysines and followed by a single glycine residue, were inserted between the neck linker (red) and the neck coiled-coil domains (gray). As examples, insertions (black) of 2, 4, 6, 13, 19, 26 prolines (2P, 4P, 6P, 13P, 19P, and 26P) are expected to extend the neck linker length to 4.7, 5.4, 6, 8, 10, and 12 nm, respectively. The insert of seven repeats of glycine and serine (14GS) is depicted as a flexible 6 nm linker.(B) and (C) Average run lengths and speeds of single GFP-tagged kinesin molecules at 1 mM ATP (mean ± SEM, N = 110–187).(D) Maximum ATP turnover rates of GFP-tagged kinesin dimers are similar at saturating microtubule concentrations (mean ± SEM, N = 3 protein preparations).(E) Calculated coupling ratio of mechanical stepping to ATP hydrolysis. See Supplemental Experimental Procedures for details of these calculations.