Researchers at the University of California, Davis, mapped a folded structure in the protein machine kinesin-1 that locks its legs and blocks its cargo site, explaining how cells control internal transport before activation.
Molecular Motor Mechanics Inside Nerve Cells
Nerve cells stretch far beyond their centers, requiring a constant supply of materials delivered along microtubules. A protein machine called kinesin-1 handles this transport, moving with two short legs that can take about 100 steps each second. Each step uses energy from ATP, allowing the motor to break the molecule and move forward along the cellular highways.
While biologists understood how kinesin-1 walked since its discovery in the 1980s, the mechanism preventing it from walking at the wrong time remained unclear for decades. The motor resembles the enchanted broomstick in The Sorcerer’s Apprentice, moving in one direction once turned on by the cell. Uncontrolled movement can cause serious effects in nerve cells, which rely on precise deliveries of neurotransmitters to communicate with thousands of other cells.
Cryo-EM Reveals a Double-Lock System
Led by associate professor of molecular and cellular biology Jawdat Al-Bassam and postdoctoral fellow Md Ashaduzzaman, the research team used cryo-electron microscopy to gather thousands of pictures of inactive kinesin-1. The structural work showed that the protein folds sharply in half rather than resting in a relaxed position. Its upper end wedges between its two motor legs, physically preventing normal walking.
A connector between the folded sections acts like a rubber band to hold the protein in its bent shape. This design creates a double lock that restrains the legs while simultaneously hiding the cargo attachment site. A protein called MAP7 helps break this locked state by wedging into the folded structure, loosening the connector and allowing the motor to unfold, expose its cargo section, and begin moving.
Implications for Neurological Disorders
Mutations involving kinesin-1 link to severe conditions such as amyotrophic lateral sclerosis, Charcot-Marie-Tooth Disease Type 2, and hereditary spastic paraplegia 10. The new structural map allows researchers to examine whether specific mutations weaken the connector, block MAP7, disrupt folding, or alter the cargo site. Coauthor Richard McKenney noted that having clear structures represents a major advance for drug design, though treatments remain a future goal.
The detailed findings are available in the journal bioRxiv.
Frequently Asked Questions About Kinesin-1 Research
How fast does the kinesin-1 motor move along cellular tracks?
Kinesin-1 can take about 100 steps each second as it travels along microtubule tracks inside cells.
When was kinesin-1 first identified by scientists?
Researchers first identified kinesin-1 during the 1980s, noting its tall, thin shape and mechanical movement.
What imaging technique did the UC Davis researchers use?
The research team used cryo-electron microscopy, or cryo-EM, capturing thousands of images of inactive kinesin-1 held at very low temperatures.
Which specific neurological diseases link to kinesin-1 mutations?
Mutations involving kinesin-1 have links to amyotrophic lateral sclerosis, Charcot-Marie-Tooth Disease Type 2, and hereditary spastic paraplegia 10.
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