Neck linkers: the power strokeATP bound, ADP + Pi leavingMicrotubule (13 protofilaments)Kinesin-1 on a microtubule at true scale: 25 nm across, one αβ-tubulin dimer (a dark seam) every 8 nm. The motor walks one protofilament hand over hand: the bound head takes an ATP, its neck linker snaps forward and throws the trailing head 16 nm ahead, so the cargo moves 8 nm per ATP. A force clamp on the rail in front keeps the spring at a fixed stretch: unloaded the motor runs about 800 nm/s; it slows under load and stalls near 6 pN, where one step does 48 pN·nm of work, about half the energy of an ATP. Past stall it slips backwards. The stalk is shown shorter than its 60 nm. Motion 60× slower.
8 nm每步（一个微管蛋白二聚体）per step (one tubulin dimer)1 ATP每步消耗consumed per step~800 nm/s空载速度unloaded speed~6 pN失速力stall force~1 µm脱落前平均行程mean run before detaching