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Brassinolide and β-Sitosterol Interleaflet Diffusion in an Asymmetric Plant Model Membrane
Anthony J Pane1,2, Mark K Jenness3,4, Angus S Murphy4
1Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, United States.
The Journal of Physical Chemistry Letters
|June 29, 2026
Summary
Brassinosteroids (BR), essential plant hormones, are transported across membranes via ABCB transporters. Molecular dynamics simulations reveal thermodynamic differences in BR and sterol diffusion, clarifying transport pathways.
Area of Science:
- Plant biology
- Molecular biology
- Biochemistry
Background:
- Brassinosteroids (BR) are vital steroid hormones in plants, synthesized in the endoplasmic reticulum.
- BR transport across membranes to the apoplast is poorly understood, despite the role of ABCB1 and ABCB19 transporters.
- Current structural data lacks clarity on the steroid diffusion process within membrane domains.
Purpose of the Study:
- To investigate the diffusion properties of brassinosteroids (BR) compared to beta-sitosterol.
- To elucidate the thermodynamic differences in passive transport mechanisms.
- To understand how BR interacts with membrane domains and ABCB transporters.
Main Methods:
- Utilized all-atom molecular dynamics (MD) simulations.
- Compared diffusion properties of BR and beta-sitosterol.
- Analyzed lipid-protein interactions within membrane models.
Main Results:
- Identified key thermodynamic differences in the passive transport of BR versus beta-sitosterol.
- Demonstrated distinct localization behaviors of BR in membrane leaflets due to its sterol-like structure.
- Revealed a potential pathway for BR exposure to ABCB transporter entry sites.
Conclusions:
- BR diffusion is thermodynamically distinct from sterol diffusion, impacting transport efficiency.
- Membrane lipid domains, particularly sphingolipid and sterol-rich outer leaflets, influence BR translocation.
- This study provides mechanistic insights into BR transport, crucial for understanding plant growth and development.
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