How do molecular motors move in one direction?

Each cycle of ATP binding and hydrolysis drives a shape change in the motor that produces a step in a fixed direction along the polar filament, so the motor walks consistently one way.

What is the difference between kinesin and dynein?

Both move along microtubules, but kinesins generally transport cargo toward the plus ends at the cell periphery, while dyneins move toward the minus ends near the cell center.

Molecular Motors and Motility

Molecular motors are proteins that convert the chemical energy of ATP into directed movement along cytoskeletal tracks, powering transport, contraction, and cell motility.

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Definition

A molecular motor is a protein that uses energy from ATP hydrolysis to move processively or generate force along a cytoskeletal filament.

Scope

This topic covers the three major motor families, myosins on actin and kinesins and dyneins on microtubules, how they couple ATP hydrolysis to mechanical steps, and how they drive cargo transport, muscle and cytoplasmic contraction, ciliary beating, and whole-cell movement.

Core questions

How do motor proteins convert ATP hydrolysis into directed motion?
What distinguishes myosins, kinesins, and dyneins?
How do motors carry cargo and produce contraction?
How do motors power processes like ciliary beating and cell crawling?

Key theories

Motor proteins as mechanochemical engines: Motors couple cycles of ATP binding, hydrolysis, and product release to conformational changes that produce directed steps along a filament, with kinesin established as a microtubule-based force generator.

Mechanisms

Each motor has a head that binds a cytoskeletal filament and hydrolyzes ATP; cycles of nucleotide binding, hydrolysis, and release drive conformational changes that move the motor in a fixed direction. Myosins act on actin to produce muscle contraction and cortical movements, kinesins generally walk toward microtubule plus ends carrying cargo outward, and dyneins move toward minus ends and power ciliary and flagellar beating. Coordinated motor activity transports organelles, positions structures, and contributes to cell motility.

Clinical relevance

Molecular motors explain how cells generate movement and organize transport at the molecular level, a foundational topic linking cell biology with biophysics. The treatment here is descriptive and non-prescriptive.

History

Huxley's sliding-filament work revealed myosin-driven muscle contraction; the 1985 identification of kinesin by Vale and Sheetz and subsequent single-molecule studies established how motors walk along filaments and power transport.

Key figures

Ronald Vale
Michael Sheetz
Hugh Huxley
James Spudich

Seminal works

vale1985
alberts2014

Frequently asked questions

How do molecular motors move in one direction?: Each cycle of ATP binding and hydrolysis drives a shape change in the motor that produces a step in a fixed direction along the polar filament, so the motor walks consistently one way.
What is the difference between kinesin and dynein?: Both move along microtubules, but kinesins generally transport cargo toward the plus ends at the cell periphery, while dyneins move toward the minus ends near the cell center.