Fluorogenic and genetic targeting of a red-emitting molecular calcium indicator

We introduce a strategy for the fluorogenic and genetic targeting of a calcium indicator by combining a protein fluorogen with the BAPTA sensing group. The resulting dual-input probe acts like a fluorescent AND logic gate with a Ca2+-sensitive red emission that is activated only upon reaction with HaloTag with a 25-fold intensity enhancement and can be used for wash-free calcium imaging in HeLa cells. The modular all-molecular design relying on a well-established self-labeling protein tag opens future possibilities for tuning the photophysical properties or targeting different analytes.

Automated summary

We present a strategy that combines a protein fluorogen with the BAPTA sensing group for fluorogenic and genetic targeting of a calcium indicator. The resulting dual-input probe behaves like a fluorescent AND logic gate, with a red emission sensitive to Ca2+ that is activated only upon reaction with HaloTag, showing a 25-fold intensity enhancement. This probe can be used for wash-free calcium imaging in HeLa cells. The modular design, based on a well-established self-labeling protein tag, allows for potential tuning of photophysical properties or targeting of different analytes.