"A Tunable Protein Piston that Breaks Membranes to Release Encapsulated Cargo"
ACS Synthetic Biology
Earth’s critters have developed countless ways to survive. Some bacteria that live inside paramecia, which are tiny aquatic organisms, use a coiled protein ribbon that unfurls like a Chinese paper yo-yo to deliver a toxin to threatening organisms. The protein packs a punch, bursting through membranes of the paramecia’s competitors as it elongates. Now, in the journal ACS Synthetic Biology, scientists report that the protein could someday deliver drugs or become integrated into tiny devices.
In a search for methods to deliver pharmaceuticals or program cells, researchers have figured out how to package drugs, DNA and RNA into little biological pouches called vesicles. Getting them out to do their job in a cell, however, is another challenge. So, scientists have looked to a strain of paramecium that deploys hitchhiking bacteria to fight off other strains. The bacteria contain coiled protein polymers called R bodies that, once inside a target organism, unroll into tubes that puncture internal membranes to release bacterial toxins. Pamela A. Silver and Jessica K. Polka wanted to see if they could tune R bodies for potential use in cellular engineering.
The researchers found that they could control the sensitivity of R bodies, making them unfurl at higher or lower pH. Lab testing on E. coli showed the proteins could burst open 60 percent of bacterial cells in acidic conditions. Because they work rapidly and reversibly, the researchers say the R bodies could be used in a variety of biotechnology applications to target the delivery of molecules inside living systems. The proteins could also serve as switches in microelectromechanical systems, or MEMS.
Watch how the proteins work in this Headline Science video.