Figure 6. Role of Neck Linker in Kinesin Stepping(A) Kinesin's native neck linker sequence was replaced by 19 proline residues (19P-NL).(B) A kymograph shows that the fluorescently tagged 19P-NL construct does not move along axonemes with 1 mM ATP.(C) Under 6 pN external load, 19P-NL showed processive movement in both directions. The insert shows that the force-induced kinesin movement occurs by consecutive 8 nm displacements and not by slippages along the microtubule axis. The motor moved faster under 1 mM ATP (black traces), compared with no nucleotide condition (red traces). Bar graph shows the measured velocities (mean ± SEM, N = 40–70).