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Updated: Dec 13, 2025
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Dissecting Mechanoenzymatic Properties of Processive Myosins with Ultrafast Force-Clamp Spectroscopy
Published on: July 1, 2021
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The SecA motor generates mechanical force during protein translocation.
Riti Gupta1, Dmitri Toptygin2, Christian M Kaiser3,4
1CMDB Graduate Program, Johns Hopkins University, 3400 N Charles St., Baltimore, MD, 21218, USA.
Nature Communications
|August 1, 2020
Summary
The SecA motor actively unfolds proteins during translocation across membranes, generating significant mechanical force. This process is crucial for efficiently exporting structured proteins in all cells.
Area of Science:
- Cellular biology
- Molecular mechanisms of protein transport
- Biophysics
Background:
- The Sec translocon facilitates protein transport across lipid bilayers in all cells.
- SecA, a cytosolic ATPase, drives protein passage through the bacterial plasma membrane channel.
- It remains unknown if SecA generates mechanical force to translocate structured proteins.
Purpose of the Study:
- To investigate whether SecA generates mechanical force to overcome translocation barriers posed by structured proteins.
- To kinetically and mechanically dissect Sec-dependent protein translocation.
Main Methods:
- High time-resolution kinetic analysis of translocating proteins with tunable stability.
- Single-molecule force spectroscopy to measure protein response to mechanical force.
Main Results:
- Substrate protein unfolding is the rate-limiting step in translocation.
- SecA generates at least 10 piconewtons of mechanical force to actively unfold proteins.
- This force is comparable to that generated by cellular unfoldases.
Conclusions:
- SecA acts as a mechanical motor, actively unfolding proteins during translocation.
- Combining kinetic and force measurements elucidates SecA's mechanism for robust protein export.
- This mechanism ensures efficient translocation of proteins with stable structures.
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