Pre-transition effects mediate forces of assembly between transmembrane proteins

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Abstract

We present a mechanism for a generic, powerful force of assembly and mobility for transmembrane proteins in lipid bilayers. This force is a pre-transition (or pre-melting) effect for the first-order transition between ordered and disordered phases in the membrane. Using large-scale molecular simulation, we show that a protein with hydrophobic thickness equal to that of the disordered phase embedded in an ordered bilayer stabilizes a microscopic order-disorder interface. The stiffness of that interface is finite. When two such proteins approach each other, they assemble because assembly reduces the net interfacial energy. Analogous to the hydrophobic effect, we refer to this phenomenon as the 'orderphobic effect'. The effect is mediated by proximity to the order-disorder phase transition and the size and hydrophobic mismatch of the protein. The strength and range of forces arising from this effect are significantly larger than those that could arise from membrane elasticity for the membranes considered.

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Shachi Katira

Department of Chemistry, University of California, Berkeley, Berkeley, United States

Competing interests
The authors declare that no competing interests exist.
Kranthi K Mandadapu

Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, United States

Competing interests
The authors declare that no competing interests exist.
Suriyanarayanan Vaikuntanathan

Department of Chemistry, University of Chicago, Chicago, United States

Competing interests
The authors declare that no competing interests exist.
Berend Smit

Department of Chemistry, University of California, Berkeley, Berkeley, United States

Competing interests
The authors declare that no competing interests exist.
David Chandler

Department of Chemistry, University of California, Berkeley, Berkeley, United States

For correspondence
chandler@berkeley.edu

Competing interests
The authors declare that no competing interests exist.

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This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.