Very recently Zhao et al.1 reported the long awaited development of RGECO, a red fluorescent protein (RFP) based Ca2+ biosensor, which originated from mApple. It was determined that it operates under a pKa modulation mechanism, whereby binding of Ca2+ lowers the chromophore's pKa, resulting in an increased fluorescence signal.The work that will be discussed is the development and characterization of another RFP-based Ca2+ biosensor. This biosensor originated from mCherry and operates by a mechanism distinct from RGECO. Upon closer examination it was determined that Ca2+ binding modulated the quantum yield and extinction coefficient. The characterization and performance of the sensor will be discussed, as well as some preliminary mechanistic exploration. Site directed mutagenesis was used to probe the involvement of several amino acid side chains. It is believed that Glu215 is the key residue that gives rise to this sensor's unique behavior.1. Zhao Y. et al. Science, 2011, 333  , 1888-1891.

Red fluorescent protein Ca<sup>2+ </sup>indicator based on quantum yield and extinction coefficent modulation

243rd National Meeting (2012)

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Red fluorescent protein Ca2+ indicator based on quantum yield and extinction coefficent modulation

Red fluorescent protein Ca²⁺indicator based on quantum yield and extinction coefficent modulation