Since AND and OR gates generate a response based on two different inputs, either together or separately, the researchers needed two different CID systems that didn't compete or overlap with each other. They relied on one system that's been studied for years, which brings two proteins, called FRB and FKBP, together in the presence of a drug called rapamycin. Rapamycin comes from bacteria, and FRB and FKBP come from animals.
In addition, they used a second CID system that brings together two other proteins, known as GID1 and GAI, in the presence of a plant hormone called gibberellin. Since this system is native to plants, the gibberellin-based system doesn't compete with the rapamycin-based one, Inoue explains.
The researchers engineered mammalian cells that produce all four of the requisite proteins, as well as a response when the right two proteins came together. When either FRB and FKBP or GID1 and GAI linked up, the cell's membrane developed ruffles easily visible under a microscope.
To create the OR gate, FRB and GAI were bound together at the cell membrane, while FKBP and GID1 were bound together floating freely in the cell. Adding either rapamycin, gibberellin, or both to cells brought the freely floating complex to the one at the cellular membrane, linking up the matching proteins and triggering the output signal.
To create the AND gate, the researchers placed just GAI at the cell membrane, with just FRB and complexes of FKBP and GID1 free-floating in the cell. This system required all four proteins to link up to produce membrane ruffling, which wouldn't occur without both input chemicals.
Tests showed that each of the engineered cellular logic gates produced the desired response reliably, in a matte
|Contact: Audrey Huang|
Johns Hopkins Medical Institutions