Biotechnology and Biological Sciences Research Council (BBSRC)
United Kingdom
American Heart Association
United States
Medical Research Council (MRC, United Kingdom)
United Kingdom
British Heart Foundation
United Kingdom
Citation
Journal: Nature / Year: 2025 Title: Swinging lever mechanism of myosin directly shown by time-resolved cryo-EM. Authors: David P Klebl / Sean N McMillan / Cristina Risi / Eva Forgacs / Betty Virok / Jennifer L Atherton / Sarah A Harris / Michele Stofella / Donald A Winkelmann / Frank Sobott / Vitold E Galkin / ...Authors: David P Klebl / Sean N McMillan / Cristina Risi / Eva Forgacs / Betty Virok / Jennifer L Atherton / Sarah A Harris / Michele Stofella / Donald A Winkelmann / Frank Sobott / Vitold E Galkin / Peter J Knight / Stephen P Muench / Charlotte A Scarff / Howard D White / Abstract: Myosins produce force and movement in cells through interactions with F-actin. Generation of movement is thought to arise through actin-catalysed conversion of myosin from an ATP-generated primed ...Myosins produce force and movement in cells through interactions with F-actin. Generation of movement is thought to arise through actin-catalysed conversion of myosin from an ATP-generated primed (pre-powerstroke) state to a post-powerstroke state, accompanied by myosin lever swing. However, the initial, primed actomyosin state has never been observed, and the mechanism by which actin catalyses myosin ATPase activity is unclear. Here, to address these issues, we performed time-resolved cryogenic electron microscopy (cryo-EM) of a myosin-5 mutant having slow hydrolysis product release. Primed actomyosin was predominantly captured 10 ms after mixing primed myosin with F-actin, whereas post-powerstroke actomyosin predominated at 120 ms, with no abundant intermediate states detected. For detailed interpretation, cryo-EM maps were fitted with pseudo-atomic models. Small but critical changes accompany the primed motor binding to actin through its lower 50-kDa subdomain, with the actin-binding cleft open and phosphate release prohibited. Amino-terminal actin interactions with myosin promote rotation of the upper 50-kDa subdomain, closing the actin-binding cleft, and enabling phosphate release. The formation of interactions between the upper 50-kDa subdomain and actin creates the strong-binding interface needed for effective force production. The myosin-5 lever swings through 93°, predominantly along the actin axis, with little twisting. The magnitude of lever swing matches the typical step length of myosin-5 along actin. These time-resolved structures demonstrate the swinging lever mechanism, elucidate structural transitions of the power stroke, and resolve decades of conjecture on how myosins generate movement.
Name: Primed actomyosin-5a complex / type: complex / ID: 1 / Parent: 0 / Macromolecule list: #1-#2 Details: F-actin decorated with primed actomyosin-5a - F-actin was mixed with myosin-5a (S1 1 IQ motif, residues 1-797, S217A, DDEK 594-597 deletion) that had been pre-incubated with ATP, and ...Details: F-actin decorated with primed actomyosin-5a - F-actin was mixed with myosin-5a (S1 1 IQ motif, residues 1-797, S217A, DDEK 594-597 deletion) that had been pre-incubated with ATP, and vitrified at 10 ms post-mixing
Model: Quantifoil / Material: COPPER / Mesh: 300 / Support film - Material: CARBON / Support film - topology: HOLEY / Pretreatment - Type: GLOW DISCHARGE / Pretreatment - Time: 60 sec. / Pretreatment - Atmosphere: AIR / Pretreatment - Pressure: 0.01 kPa Details: 300 mesh copper grids with copper nano-wires (SPT Labtech)
Vitrification
Cryogen name: ETHANE / Chamber humidity: 60 % / Chamber temperature: 293 K / Instrument: HOMEMADE PLUNGER Details: F-actin was mixed with myosin-5a (S1 1 IQ motif, residues 1-797, S217A, DDEK 594-597 deletion) that had been pre-incubated with ATP, and vitrified at 10 ms post-mixing.
Details
Actin-myosin mixture comprising 13 uM myosin (pre-mixed with ATP) and 13 uM actin
-
Electron microscopy
Microscope
FEI TITAN KRIOS
Image recording
Film or detector model: GATAN K2 QUANTUM (4k x 4k) / Detector mode: COUNTING / Number grids imaged: 3 / Number real images: 9692 / Average exposure time: 7.0 sec. / Average electron dose: 61.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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