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Two novel FRET-pairs: Tb3+ -binding peptide-DsRed2 and Tb3+ -binding peptide-TagRFP have been produced based on the terbium-binding peptide and the red fluorescent proteins DsRed2 and TagRFP. Two induction-resonance energy transfer processes in both FRET-pairs have been registered, from tryptophan of the terbium-binding peptide to Tb3+ and from sensitized Tb3+ to the acceptor, the chromophore, DsRed2 or TagRFP. The lifetimes of terbium in the presence and absence of the acceptor have been determined. It has been shown that the lifetime of Tb3+ in the presence of 150 mM NaCl decreases in both FRET-pairs. The efficiency of fluorescent resonance transfer from Tb3+ to the acceptor proteins is 28 and 35% for Tb3+ -binding peptide-DsRed2 and Tb3+ -binding peptide-TagRFP, respectively.

The genetically encoded FRET-pair was developed on the basis of terbium-binding peptide and red fluorescent protein DsRed2. To study fluorescence resonance energy transfer within FRET-pair, the gene-engineered construction was obtained, where sequences of terbium-binding peptide and red fluorescent protein DsRed2 were fused in single reading frame. The expression of this construction in strain E. coli BL21 (DE3) was studied and conditions of synthesis, isolation and purification of recombinant protein were optimized. The hydrodynamic radius of hybrid protein was determined by the method of dynamic light scattering. Energy transfer between sensitized terbium and red fluorescent protein was confirmed by the methods of phosporescent spectroscopy. The obtained FRET-pair can be used both for studies in vitro and as a reporter in living cells.