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ACS Synth Biol. 2016 Apr 15;5(4):303-11. doi: 10.1021/acssynbio.5b00237. Epub 2016 Feb 3.

A Tunable Protein Piston That Breaks Membranes to Release Encapsulated Cargo.

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Department of Systems Biology, Harvard Medical School , Boston, Massachusetts 02115, United States.
Wyss Institute for Biologically Inspired Engineering , Boston, Massachusetts 02115, United States.


Movement of molecules across membranes in response to a stimulus is a key component of cellular programming. Here, we characterize and manipulate the response of a protein-based piston capable of puncturing membranes in a pH-dependent manner. Our protein actuator consists of modified R bodies found in a bacterial endosymbiont of paramecium. We express and purify R bodies from in E. coli; these pistons undergo multiple rounds of rapid extension and retraction. We developed a high throughput screen for mutants with altered pH sensitivity for tuning of the extension process. We show that the R bodies are capable of acting as synthetic pH-dependent pistons that can puncture E. coli membranes to release the trapped content. As such, these protein machines present a novel way to selectively rupture membrane compartments and will be important for programming cellular compartmentalization.


Kappa particles; bioengineering; biotechnology; conformational change; protein assembly; refractile bodies

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