Evolving infrared fluorescent proteins from Bacterial phytochrome – a new direction for rational engineering photochemical transducers

More than 1500 bacteriophytochrome-like sequences are already available in the National Center for Biotechnology Information (NIH) and CAMERA databases (28). These genes should provide raw material for selection and directed evolution of photochemical transducers based on a scaffold completely independent of the 11-stranded β barrel of coelenterate FPs.

Brain Windows is presenting a recent paper from Roger Tsien’s lab about an infrared fluorescent protein IFP1.4. Check it out!

Science 8 May 2009:
Vol. 324. no. 5928, pp. 804 – 807
DOI: 10.1126/science.1168683

Mammalian Expression of Infrared Fluorescent Proteins Engineered from a Bacterial Phytochrome

Xiaokun Shu,1,2 Antoine Royant,3 Michael Z. Lin,2 Todd A. Aguilera,2 Varda Lev-Ram,2 Paul A. Steinbach,1,2 Roger Y. Tsien1,2,4,*

Visibly fluorescent proteins (FPs) from jellyfish and corals have revolutionized many areas of molecular and cell biology, but the use of FPs in intact animals, such as mice, has been handicapped by poor penetration of excitation light. We now show that a bacteriophytochrome from Deinococcus radiodurans, incorporating biliverdin as the chromophore, can be engineered into monomeric, infrared-fluorescent proteins (IFPs), with excitation and emission maxima of 684 and 708 nm, respectively; extinction coefficient >90,000 M–1 cm–1; and quantum yield of 0.07. IFPs express well in mammalian cells and mice and spontaneously incorporate biliverdin, which is ubiquitous as the initial intermediate in heme catabolism but has negligible fluorescence by itself. Because their wavelengths penetrate tissue well, IFPs are suitable for whole-body imaging. The IFPs developed here provide a scaffold for further engineering.

1 Howard Hughes Medical Institute, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093–0647, USA.
2 Department of Pharmacology, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093–0647, USA.
3 Institut de Biologie Structurale 41, rue Jules Horowitz, 38027 Grenoble CEDEX 1, France.
4 Departments of Chemistry and Biochemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093–0647, USA.

* To whom correspondence should be addressed. E-mail: rtsien@ucsd.edu