Peculiarities of the prime structures of the red fluorescent proteins that change their fluorescent spectra with time

Abstract

By the directed sight-specific and accidental mutagenesis of the red fluorescent protein mCherry, 3 mutant
proteins have been developed, named fluorescent timers (FT), which, in contrast to initial protein, change their fluorescence from blue to red. Their prime structures have been determined. Isolated mutant proteins differ one from another by the rate of the fluorescence spectra changes with the different rate: fast (FFT), Medium (MFT), and Slow (SFT). In comparison with initial mCherry FFT contains 5 amino acid replacements.
Lys→Arg, Leu→Trp, Ala→Ser at 69, 84 & 224 positions are internal, and Glu→Lys, Ser→Thr at 34 and 15
positions are situated at the external surface of the protein. In the amino acid sequence of MFT, there have been found 9 substitutions. Replacements Lys→Arg, Leu→Trp, Met→Ile, Leu→Met at 69, 84, 152 & 205 positions are internal, Asn→Asp, Thr→Ser, Gln→Lys, Tyr→Cys, Arg→His at 23, 43, 194, 221 & 227- external. SFT has only 4 replacements. Three of them Lys→Arg, Leu→Trp, Ala→Val at 69, 84 & 179 positions are in the
inner space of the molecule, Glu→Val at 30 positions is at its surface. The structural roles of substitutions that have been found are discussed in relation to the fluorescent properties of FFT, MFT, and SFT and their difference from the properties of mCherry and one from another.