|Ex λ||Em λ||EC (M-1 cm-1)||QY||Brightness||pKa||Maturation (min)||Lifetime (ns)|
|% Normal Cells||OSER/NE ratio||Cell Type||Reference|
|95.8 ± 1.1 (10000 cells)||-||HeLa||Cranfill et al. (2016)|
|t1/2 (s)||Power||Light||Mode||In Cell||Fusion||˚C||Reference|
|6.2||Shaner et al. (2004)|
mRFP1 was derived from dimer1 with the following mutations: V1adel/V71A/K83L/C117E/F124L/V127T/L150M/R153E/V156A/H162K/Q163M/A164R/L174D/V175A/F177V/I180T/Y192A/Y194K/V195T/T197I/H222S/L223T/F224G/L225A
amino acid numbers relative to DsRed. show relative to dimer1
We present here the stepwise evolution of DsRed to a dimer and then either to a genetic fusion of two copies of the protein, i.e., a tandem dimer, or to a true monomer designated mRFP1 (monomeric red fluorescent protein). Each subunit interface was disrupted by insertion of arginines, which initially crippled the resulting protein, but red fluorescence could be rescued by random and directed mutagenesis totaling 17 substitutions in the dimer and 33 in mRFP1.
Although mRFP1 has somewhat lower extinction coefficient, quantum yield, and photostability than DsRed, mRFP1 matures >10 times faster, so that it shows similar brightness in living cells.
Our basic strategy for decreasing the oligomeric state of DsRed was to replace key dimer interface residues with arginine. When the targeted residue interacts with the identical residue of the dimer partner through symmetry, the high energetic cost of placing two positive charges in close proximity should disrupt the interaction. Such a strategy disrupted the weak tendency of wtGFP to dimerize, without any deleterious effects on GFP maturation or brightness (Zacharias et al. 2002).