{"format":"molecular-machines.cards","version":1,"updated":"2026-10-01","decks":[{"machine":"kinesin","name":"Kinesin","count":28,"url":"/learn/cards/kinesin.json"}],"cards":[{"id":"kinesin-direction","machine":"kinesin","kind":"qa","prompt":"Which way along a microtubule does kinesin-1 carry its cargo?","answer":"Toward the plus end.","explanation":"Its two heads take turns: the rear head swings past the bound head and lands 16 nm ahead.","section":"summary","topic":"purpose","sources":["machine:summary","machine:tagline"],"tags":["direction","transport"],"difficulty":1,"url":"/machines/kinesin#summary","cites":[{"source":"machine:summary","machine":"kinesin","label":"Summary","section":"summary"},{"source":"machine:tagline","machine":"kinesin","label":"Summary","section":"summary"}]},{"id":"kinesin-neck-linker-role","machine":"kinesin","kind":"qa","prompt":"Which part of kinesin-1 docks onto the head when ATP binds and pulls the partner head forward?","answer":"The neck linker.","explanation":"It is a short segment of about 13-15 residues after helix α6; papers draw its boundaries differently.","section":"summary","topic":"parts","sources":["component:neck linker","stat:Neck linker","ref:rice1999"],"tags":["neck-linker","parts"],"difficulty":1,"url":"/machines/kinesin#summary","cites":[{"source":"component:neck linker","machine":"kinesin","label":"Part: neck linker","section":"summary"},{"source":"stat:Neck linker","machine":"kinesin","label":"Key number: Neck linker","section":"summary"},{"source":"ref:rice1999","machine":"kinesin","label":"Rice et al.","section":"sources","anchor":"ref-rice1999","href":"https://doi.org/10.1038/45483"}]},{"id":"kinesin-direction-from-neck","machine":"kinesin","kind":"qa","prompt":"Plus-end and minus-end kinesins have nearly identical cores. Which part of a kinesin sets the direction it walks?","answer":"The neck next to the core.","explanation":"Swapping necks or domain order reverses motion, so the core alone does not set direction.","section":"summary","topic":"parts","sources":["evolution:Direction from the neck","ref:endow1998","ref:case1997"],"tags":["direction","evolution"],"difficulty":2,"url":"/machines/kinesin#summary","cites":[{"source":"evolution:Direction from the neck","machine":"kinesin","label":"Direction from the neck","section":"summary"},{"source":"ref:endow1998","machine":"kinesin","label":"Endow et al.","section":"sources","anchor":"ref-endow1998","href":"https://doi.org/10.1126/science.281.5380.1200"},{"source":"ref:case1997","machine":"kinesin","label":"Case et al.","section":"sources","anchor":"ref-case1997","href":"https://doi.org/10.1016/s0092-8674(00)80360-8"}]},{"id":"kinesin-step-size","machine":"kinesin","kind":"cloze","prompt":"Kinesin-1's centre of mass moves {{8 nm}} per step, the length of one tubulin dimer.","answer":"8 nm","explanation":"Each head moves about twice as far (17.3 ± 3.3 nm), because the heads pass each other.","section":"summary","topic":"numbers","sources":["stat:Step size","stat:Head step","ref:svoboda1993"],"tags":["step","numbers"],"difficulty":1,"url":"/machines/kinesin#summary","cites":[{"source":"stat:Step size","machine":"kinesin","label":"Key number: Step size","section":"summary"},{"source":"stat:Head step","machine":"kinesin","label":"Key number: Head step","section":"summary"},{"source":"ref:svoboda1993","machine":"kinesin","label":"Svoboda et al.","section":"sources","anchor":"ref-svoboda1993","href":"https://doi.org/10.1038/365721a0"}]},{"id":"kinesin-steps-per-run","machine":"kinesin","kind":"qa","prompt":"About how many steps does a single kinesin-1 take before it lets go of the microtubule?","answer":"About 100 (a run of about 1 µm).","explanation":"The fitted run length at zero load is 1.12 µm, which is more than 100 steps per encounter with the microtubule.","section":"summary","topic":"numbers","sources":["stat:Run length","machine:summary","ref:milic2014"],"tags":["processivity","numbers"],"difficulty":2,"url":"/machines/kinesin#summary","cites":[{"source":"stat:Run length","machine":"kinesin","label":"Key number: Run length","section":"summary"},{"source":"machine:summary","machine":"kinesin","label":"Summary","section":"summary"},{"source":"ref:milic2014","machine":"kinesin","label":"Milic et al.","section":"sources","anchor":"ref-milic2014","href":"https://doi.org/10.1073/pnas.1410943111"}]},{"id":"kinesin-turnover-time","machine":"kinesin","kind":"cloze","prompt":"With no load, kinesin-1 walks at about 800 nm/s, so one turnover takes about {{10 ms}}.","answer":"10 ms","explanation":"At 8 nm per step, 800 nm/s is about 100 steps per second.","section":"summary","topic":"numbers","sources":["stat:Velocity, no load","fact:s-speed","ref:verbrugge2007"],"tags":["speed","numbers"],"difficulty":2,"url":"/machines/kinesin#summary","cites":[{"source":"stat:Velocity, no load","machine":"kinesin","label":"Key number: Velocity, no load","section":"summary"},{"source":"fact:s-speed","machine":"kinesin","label":"Walking speed with no load: 800 nm/s","section":"story"},{"source":"ref:verbrugge2007","machine":"kinesin","label":"Verbrugge et al.","section":"sources","anchor":"ref-verbrugge2007","href":"https://doi.org/10.1529/biophysj.106.093575"}]},{"id":"kinesin-molecular-shuttle","machine":"kinesin","kind":"qa","prompt":"In a kinesin 'molecular shuttle', what does the kinesin do?","answer":"It is fixed on a surface and pushes microtubules that carry cargo.","explanation":"Surface patterns steer the microtubules, and the ATP supply sets their speed. This use is demonstrated.","section":"summary","topic":"debate","sources":["frontier:Molecular shuttles","ref:hess2001"],"tags":["frontier","engineering"],"difficulty":2,"url":"/machines/kinesin#summary","cites":[{"source":"frontier:Molecular shuttles","machine":"kinesin","label":"Open question: Molecular shuttles","section":"summary"},{"source":"ref:hess2001","machine":"kinesin","label":"Hess et al.","section":"sources","anchor":"ref-hess2001","href":"https://doi.org/10.1016/s1389-0352(01)00029-0"}]},{"id":"kinesin-designed-motor","machine":"kinesin","kind":"qa","prompt":"Unlike kinesin, how does a designed protein motor (a protease-coated hub) move across a peptide lawn?","answer":"By cutting the path behind it.","explanation":"It reaches up to 80 nm/s. Designed protein motors are now possible at lab scale, but they are simpler than kinesin.","section":"summary","topic":"debate","sources":["frontier:Designed protein motors","ref:korosec2024"],"tags":["frontier","design"],"difficulty":2,"url":"/machines/kinesin#summary","cites":[{"source":"frontier:Designed protein motors","machine":"kinesin","label":"Open question: Designed protein motors","section":"summary"},{"source":"ref:korosec2024","machine":"kinesin","label":"Korosec et al.","section":"sources","anchor":"ref-korosec2024","href":"https://doi.org/10.1038/s41467-024-45570-y"}]},{"id":"kinesin-atp-docks-linker","machine":"kinesin","kind":"cloze","prompt":"In kinesin-1, {{ATP binding}} to the bound head makes its neck linker zip onto the head.","answer":"ATP binding","explanation":"This docking is the power stroke: the neck linker ends up pointing to the plus end.","section":"mechanism","topic":"cycle","sources":["mechanism:ATP docks the neck linker","step:ATP binds and the neck linker zips","ref:rice1999"],"tags":["neck-linker","atp","power-stroke"],"difficulty":1,"url":"/machines/kinesin#mechanism","cites":[{"source":"mechanism:ATP docks the neck linker","machine":"kinesin","label":"Step: ATP docks the neck linker","section":"mechanism"},{"source":"step:ATP binds and the neck linker zips","machine":"kinesin","label":"Step: ATP binds and the neck linker zips","section":"mechanism"},{"source":"ref:rice1999","machine":"kinesin","label":"Rice et al.","section":"sources","anchor":"ref-rice1999","href":"https://doi.org/10.1038/45483"}]},{"id":"kinesin-why-docking-needs-atp","machine":"kinesin","kind":"qa","prompt":"Why do ATP binding and neck-linker docking go together in a kinesin-1 head?","answer":"Only the closed, ATP-bound head offers the groove the neck linker docks into.","explanation":"Closing the nucleotide pocket turns two parts of the head (by about 22° and 11°), and that opens a groove along the head.","section":"mechanism","topic":"cycle","sources":["step:ATP binds and the neck linker zips"],"tags":["neck-linker","atp"],"difficulty":3,"url":"/machines/kinesin#mechanism","cites":[{"source":"step:ATP binds and the neck linker zips","machine":"kinesin","label":"Step: ATP binds and the neck linker zips","section":"mechanism"}]},{"id":"kinesin-diffusion-search","machine":"kinesin","kind":"cloze","prompt":"In a kinesin-1 step, {{diffusion}} carries the free head forward; neck-linker docking only sets the direction.","answer":"diffusion","explanation":"The docked neck linker of the bound head holds the tethered head near the forward site, and it lands about 16 nm ahead.","section":"mechanism","topic":"cycle","sources":["step:The free head searches","mechanism:The rear head swings forward","ref:yildiz2004"],"tags":["diffusion","stepping"],"difficulty":2,"url":"/machines/kinesin#mechanism","cites":[{"source":"step:The free head searches","machine":"kinesin","label":"Step: The free head searches","section":"mechanism"},{"source":"mechanism:The rear head swings forward","machine":"kinesin","label":"Step: The rear head swings forward","section":"mechanism"},{"source":"ref:yildiz2004","machine":"kinesin","label":"Yildiz et al.","section":"sources","anchor":"ref-yildiz2004","href":"https://doi.org/10.1126/science.1093753"}]},{"id":"kinesin-adp-release-trigger","machine":"kinesin","kind":"qa","prompt":"What makes a kinesin-1 head release its ADP?","answer":"Binding the microtubule, which opens the nucleotide cleft.","explanation":"A dimer that lands on a microtubule releases only one of its two ADPs, so one head binds the track and the other stays free.","section":"mechanism","topic":"cycle","sources":["mechanism:One head holds the track","step:The front head waits for ATP","ref:shang2014"],"tags":["adp","microtubule"],"difficulty":2,"url":"/machines/kinesin#mechanism","cites":[{"source":"mechanism:One head holds the track","machine":"kinesin","label":"Step: One head holds the track","section":"mechanism"},{"source":"step:The front head waits for ATP","machine":"kinesin","label":"Step: The front head waits for ATP","section":"mechanism"},{"source":"ref:shang2014","machine":"kinesin","label":"Shang et al.","section":"sources","anchor":"ref-shang2014","href":"https://doi.org/10.7554/eLife.04686"}]},{"id":"kinesin-adp-weak-binding","machine":"kinesin","kind":"cloze","prompt":"A kinesin-1 head holding {{ADP}} binds the track only weakly, so it can search or let go.","answer":"ADP","explanation":"A head with an empty pocket grips the track tightly, so the new front head anchors the motor before the rear head lets go.","section":"mechanism","topic":"cycle","sources":["step:The rear head lets go","step:The free head searches","step:It lands and releases ADP"],"tags":["adp","gating"],"difficulty":2,"url":"/machines/kinesin#mechanism","cites":[{"source":"step:The rear head lets go","machine":"kinesin","label":"Step: The rear head lets go","section":"mechanism"},{"source":"step:The free head searches","machine":"kinesin","label":"Step: The free head searches","section":"mechanism"},{"source":"step:It lands and releases ADP","machine":"kinesin","label":"Step: It lands and releases ADP","section":"mechanism"}]},{"id":"kinesin-phosphate-gate","machine":"kinesin","kind":"qa","prompt":"Why does kinesin-1 stay on the track for about 100 steps instead of falling off after one?","answer":"The rear head lets go only after phosphate leaves, and by then the front head is bound.","explanation":"This order keeps one head on the track at all times.","section":"mechanism","topic":"cycle","sources":["step:The rear head lets go","ref:milic2014"],"tags":["processivity","gating","phosphate"],"difficulty":3,"url":"/machines/kinesin#mechanism","cites":[{"source":"step:The rear head lets go","machine":"kinesin","label":"Step: The rear head lets go","section":"mechanism"},{"source":"ref:milic2014","machine":"kinesin","label":"Milic et al.","section":"sources","anchor":"ref-milic2014","href":"https://doi.org/10.1073/pnas.1410943111"}]},{"id":"kinesin-hydrolysis-timing-debate","machine":"kinesin","kind":"qa","prompt":"When kinesin-1 splits its ATP is still argued. What does tracking single heads at 1,000 frames per second suggest?","answer":"The bound head must split its ATP before the free head can land.","explanation":"The animation in the notes shows the split after the front head lands instead.","section":"mechanism","topic":"debate","sources":["step:The rear head hydrolyses ATP","ref:mickolajczyk2015"],"tags":["hydrolysis","debate"],"difficulty":3,"url":"/machines/kinesin#mechanism","cites":[{"source":"step:The rear head hydrolyses ATP","machine":"kinesin","label":"Step: The rear head hydrolyses ATP","section":"mechanism"},{"source":"ref:mickolajczyk2015","machine":"kinesin","label":"Mickolajczyk et al.","section":"sources","href":"https://doi.org/10.1073/pnas.1517638112"}]},{"id":"kinesin-back-step-cause","machine":"kinesin","kind":"qa","prompt":"Under a heavy opposing load, why does kinesin-1's free head land behind its partner instead of ahead?","answer":"The pull on the stalk cancels the small forward bias from neck-linker docking.","explanation":"The landing site is set by where the head is when it touches down. The chemistry is the same as a forward step, one ATP per step.","section":"mechanism","topic":"cycle","sources":["step:The load biases the search backward","step:It lands behind and releases ADP","mechanism:Load slows the motor","ref:carter2005"],"tags":["load","back-steps"],"difficulty":3,"url":"/machines/kinesin#mechanism","cites":[{"source":"step:The load biases the search backward","machine":"kinesin","label":"Step: The load biases the search backward","section":"mechanism"},{"source":"step:It lands behind and releases ADP","machine":"kinesin","label":"Step: It lands behind and releases ADP","section":"mechanism"},{"source":"mechanism:Load slows the motor","machine":"kinesin","label":"Step: Load slows the motor","section":"mechanism"},{"source":"ref:carter2005","machine":"kinesin","label":"Carter et al.","section":"sources","anchor":"ref-carter2005","href":"https://doi.org/10.1038/nature03528"}]},{"id":"kinesin-drift-time","machine":"kinesin","kind":"cloze","prompt":"If proteins made near the spine just drifted down a 1 m nerve cell, they would need about {{300 years}} to reach the foot.","answer":"300 years","explanation":"Diffusion time grows with the square of distance: about two weeks for 1 cm becomes about 300 years for 1 m. Kinesin motors make the trip in a few days.","section":"story","topic":"purpose","sources":["fact:K2","stop:race","ref:cbtn-diffusion"],"tags":["axon","diffusion"],"difficulty":2,"url":"/machines/kinesin#story","cites":[{"source":"fact:K2","machine":"kinesin","label":"Time for a protein to drift 1 m by diffusion: 300 years","section":"story"},{"source":"stop:race","machine":"kinesin","label":"Big picture: Drift or motor","section":"story"},{"source":"ref:cbtn-diffusion","machine":"kinesin","label":"Cell Biology by the Numbers","section":"sources","href":"https://book.bionumbers.org/what-are-the-time-scales-for-diffusion-in-cells/"}]},{"id":"kinesin-fast-transport-time","machine":"kinesin","kind":"qa","prompt":"About how long does fast outward transport take to carry cargo 1 m along a nerve cell?","answer":"About 2.5-5 days.","explanation":"Fast outward transport runs at 200-400 mm per day (2-5 µm/s).","section":"story","topic":"numbers","sources":["fact:K3","ref:brown2003"],"tags":["axon","transport"],"difficulty":2,"url":"/machines/kinesin#story","cites":[{"source":"fact:K3","machine":"kinesin","label":"Speed of fast outward transport in axons: 200–400 mm per day","section":"story"},{"source":"ref:brown2003","machine":"kinesin","label":"Brown 2003","section":"sources","href":"https://doi.org/10.1083/jcb.200212017"}]},{"id":"kinesin-teams-of-motors","machine":"kinesin","kind":"qa","prompt":"A single kinesin falls off after about 1 µm. How does cargo still finish a 1 m trip down an axon?","answer":"Teams of motors grab on again and again.","explanation":"One motor would let go about 10^6 times on the way; this is where the delivery-truck analogy breaks.","section":"story","topic":"purpose","sources":["analogy:A delivery truck on a highway","fact:K8"],"tags":["analogy","processivity"],"difficulty":2,"url":"/machines/kinesin#story","cites":[{"source":"analogy:A delivery truck on a highway","machine":"kinesin","label":"Analogy: A delivery truck on a highway","section":"story"},{"source":"fact:K8","machine":"kinesin","label":"Steps for one kinesin to cross 1 m: 1.25 × 10^8 steps, one ATP each","section":"story"}]},{"id":"kinesin-walker-analogy","machine":"kinesin","kind":"qa","prompt":"The 'walker with two feet' picture of kinesin gets hand-over-hand stepping right. What does it get wrong about the free foot?","answer":"It does not swing by muscle: it jiggles by heat, and the zipped neck linker only biases where it lands.","explanation":"Diffusion does the travel; docking sets the direction.","section":"story","topic":"purpose","sources":["analogy:A walker with two feet","step:The free head searches"],"tags":["analogy","diffusion"],"difficulty":2,"url":"/machines/kinesin#story","cites":[{"source":"analogy:A walker with two feet","machine":"kinesin","label":"Analogy: A walker with two feet","section":"story"},{"source":"step:The free head searches","machine":"kinesin","label":"Step: The free head searches","section":"mechanism"}]},{"id":"kinesin-dynein-tug","machine":"kinesin","kind":"qa","prompt":"On a cargo vesicle in an axon, which motor pulls against kinesin, back toward the cell body?","answer":"Dynein.","explanation":"Vesicles from mouse brain carry 1-4 kinesins and 1-5 dyneins, and the cargo moves in fits and starts.","section":"story","topic":"purpose","sources":["fact:K6","link:dynein","stop:vesicle","ref:hendricks2010"],"tags":["dynein","axon","cargo"],"difficulty":1,"url":"/machines/kinesin#story","cites":[{"source":"fact:K6","machine":"kinesin","label":"Kinesins on one brain vesicle: 1–4 kinesins","section":"story"},{"source":"link:dynein","machine":"kinesin","label":"Link to Dynein","section":"story"},{"source":"stop:vesicle","machine":"kinesin","label":"Big picture: Vesicle team","section":"story"},{"source":"ref:hendricks2010","machine":"kinesin","label":"Hendricks 2010","section":"sources","href":"https://doi.org/10.1016/j.cub.2010.02.058"}]},{"id":"kinesin-svoboda-method","machine":"kinesin","kind":"qa","prompt":"How did Svoboda and colleagues (1993) first see kinesin's 8 nm steps?","answer":"With optical trapping interferometry: they tracked a bead carried by one kinesin.","explanation":"The bead moved in discrete 8 nm steps, the length of one tubulin dimer, the repeat of the track.","section":"evidence","topic":"numbers","sources":["evidence:svoboda1993-8nm-steps","ref:svoboda1993"],"tags":["method","optical-trap","step"],"difficulty":2,"url":"/machines/kinesin#evidence","cites":[{"source":"evidence:svoboda1993-8nm-steps","machine":"kinesin","label":"Step size of single kinesin molecules (Svoboda K 1993)","section":"evidence","anchor":"ev-svoboda1993-8nm-steps"},{"source":"ref:svoboda1993","machine":"kinesin","label":"Svoboda et al.","section":"sources","anchor":"ref-svoboda1993","href":"https://doi.org/10.1038/365721a0"}]},{"id":"kinesin-hand-over-hand-proof","machine":"kinesin","kind":"qa","prompt":"Yildiz and colleagues put one dye on one head of kinesin. What pattern of dye movement showed that kinesin walks hand over hand?","answer":"The dye jumped about 17 nm, then not at all, in turn.","explanation":"Meanwhile the motor as a whole moved 8.3 nm per step, so the heads must swap places.","section":"evidence","topic":"numbers","sources":["evidence:yildiz2004-head-step","ref:yildiz2004"],"tags":["method","fluorescence","hand-over-hand"],"difficulty":2,"url":"/machines/kinesin#evidence","cites":[{"source":"evidence:yildiz2004-head-step","machine":"kinesin","label":"Step of a single labelled kinesin head (Yildiz A 2004)","section":"evidence","anchor":"ev-yildiz2004-head-step"},{"source":"ref:yildiz2004","machine":"kinesin","label":"Yildiz et al.","section":"sources","anchor":"ref-yildiz2004","href":"https://doi.org/10.1126/science.1093753"}]},{"id":"kinesin-one-atp-method","machine":"kinesin","kind":"qa","prompt":"How did Coy and colleagues (1999) show that kinesin takes one step per ATP?","answer":"They divided the bead speed by an 8.1 nm step, then by the ATP turnover of the same beads.","explanation":"Every preparation gave close to one: 1.08 ± 0.09 steps per ATP pooled.","section":"evidence","topic":"numbers","sources":["evidence:coy1999-steps-per-atp","ref:coy1999"],"tags":["method","atp","coupling"],"difficulty":3,"url":"/machines/kinesin#evidence","cites":[{"source":"evidence:coy1999-steps-per-atp","machine":"kinesin","label":"Steps per ATP hydrolysed, from speed and ATPase of the same bead-bound motors (Coy DL 1999)","section":"evidence","anchor":"ev-coy1999-steps-per-atp"},{"source":"ref:coy1999","machine":"kinesin","label":"Coy, Wagenbach and Howard, J Biol Chem 1999","section":"sources","href":"https://doi.org/10.1074/jbc.274.6.3667"}]},{"id":"kinesin-backstep-stall","machine":"kinesin","kind":"cloze","prompt":"In Carter and Cross's optical trap, kinesin-1 took as many back steps as forward steps near {{7 pN}} of opposing load.","answer":"7 pN","explanation":"That is the stall force; above it kinesin walked backward. It is higher than the 5.4 pN measured against a glass fibre.","section":"evidence","topic":"debate","sources":["evidence:carter2005-backstep-ratio","evidence:meyhofer1995-stall-force","ref:carter2005"],"tags":["stall-force","back-steps","load"],"difficulty":2,"url":"/machines/kinesin#evidence","cites":[{"source":"evidence:carter2005-backstep-ratio","machine":"kinesin","label":"Ratio of forward to backward steps against load (Carter NJ 2005)","section":"evidence","anchor":"ev-carter2005-backstep-ratio"},{"source":"evidence:meyhofer1995-stall-force","machine":"kinesin","label":"Maximum force of a single kinesin molecule against an elastic glass fibre (Meyhöfer E 1995)","section":"evidence","anchor":"ev-meyhofer1995-stall-force"},{"source":"ref:carter2005","machine":"kinesin","label":"Carter et al.","section":"sources","anchor":"ref-carter2005","href":"https://doi.org/10.1038/nature03528"}]},{"id":"kinesin-stall-vs-atp","machine":"kinesin","kind":"qa","prompt":"Visscher and colleagues (1999) measured kinesin's stall force at different ATP levels. What did they find?","answer":"The stall force rises with ATP concentration.","explanation":"So the stall force is not one fixed number. Against a glass fibre, Meyhöfer and Howard found about the same force at high and low ATP.","section":"evidence","topic":"debate","sources":["evidence:visscher1999-stall-vs-atp","evidence:meyhofer1995-stall-force","ref:visscher1999"],"tags":["stall-force","atp"],"difficulty":3,"url":"/machines/kinesin#evidence","cites":[{"source":"evidence:visscher1999-stall-vs-atp","machine":"kinesin","label":"Stall force as a function of ATP concentration (Visscher K 1999)","section":"evidence","anchor":"ev-visscher1999-stall-vs-atp"},{"source":"evidence:meyhofer1995-stall-force","machine":"kinesin","label":"Maximum force of a single kinesin molecule against an elastic glass fibre (Meyhöfer E 1995)","section":"evidence","anchor":"ev-meyhofer1995-stall-force"},{"source":"ref:visscher1999","machine":"kinesin","label":"Visscher et al.","section":"sources","anchor":"ref-visscher1999","href":"https://doi.org/10.1038/22146"}]},{"id":"kinesin-neck-charge","machine":"kinesin","kind":"qa","prompt":"Why does extra positive charge on kinesin's neck coiled coil make its runs longer?","answer":"The positive neck holds on to the negatively charged tails of tubulin.","explanation":"Runs grew about four-fold with speed unchanged. Salt, or removing the tubulin tails, cancelled the gain.","section":"evidence","topic":"numbers","sources":["evidence:neck-charge-thorn2000","ref:thorn2000"],"tags":["processivity","engineering"],"difficulty":3,"url":"/machines/kinesin#evidence","cites":[{"source":"evidence:neck-charge-thorn2000","machine":"kinesin","label":"Run length after changing the charge of the neck coiled coil (Thorn KS 2000)","section":"evidence","anchor":"ev-neck-charge-thorn2000"},{"source":"ref:thorn2000","machine":"kinesin","label":"Thorn et al.","section":"sources","anchor":"ref-thorn2000","href":"https://doi.org/10.1083/jcb.151.5.1093"}]},{"id":"kinesin-phosphate-evidence","machine":"kinesin","kind":"qa","prompt":"In Milic and colleagues' force-clamp runs, what effect of added phosphate showed that kinesin's processivity is gated by phosphate release?","answer":"Added phosphate made the runs longer.","explanation":"Under forward load, runs became up to about twice as long: the rear head lets go only after it releases phosphate.","section":"evidence","topic":"numbers","sources":["evidence:milic2014-run-length","step:The rear head lets go","ref:milic2014"],"tags":["processivity","phosphate","method"],"difficulty":3,"url":"/machines/kinesin#evidence","cites":[{"source":"evidence:milic2014-run-length","machine":"kinesin","label":"Unloaded run length of single kinesin molecules (Milic B 2014)","section":"evidence","anchor":"ev-milic2014-run-length"},{"source":"step:The rear head lets go","machine":"kinesin","label":"Step: The rear head lets go","section":"mechanism"},{"source":"ref:milic2014","machine":"kinesin","label":"Milic et al.","section":"sources","anchor":"ref-milic2014","href":"https://doi.org/10.1073/pnas.1410943111"}]}]}