Green fluorescent protein with tryptophan-based chromophore stable at low pH

Abstract

Using directed (substitution T203Y) and subsequent random mutagenesis of the monomeric cyan fluorescent protein mTurquoise2, we obtained a protein with a tryptophan-based chromophore that fluoresces in the green region of the spectrum (excitation maximum 482 nm, emission maximum 519 nm). Fluorescence of the new protein is highly stable in a wide range of pH (pK_a 4.9), more stable than all monomeric green fluorescent proteins with a tyrosine-based chromophore.