Separation of photo-induced radical pair in cryptochrome to a functionally critical distance.
Cryptochrome is a blue light receptor that acts as a sensor for the geomagnetic field and assists many animals in long-range navigation. The magnetoreceptor function arises from light-induced formation of a radical pair through electron transfer between a flavin cofactor (FAD) and a triad of tryptophan residues. Here, this electron transfer is investigated by quantum chemical and classical molecular dynamics calculations. The results reveal how sequential electron transfer, assisted by rearrangement of polar side groups in the cryptochrome interior, can yield a FAD-Trp radical pair state with the FAD and Trp partners separated beyond a critical distance. The large radical pair separation reached establishes cryptochrome's sensitivity to the geomagnetic field through weakening of distance-dependent exchange and dipole-dipole interactions. It is estimated that the key secondary electron transfer step can overcome in speed both recombination (electron back-transfer) and proton transfer involving the radical pair reached after primary electron transfer.
1] Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave, Urbana Illinois 61801, USA [2] Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
Ilia A
IA
Solov'yov
Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.
Tatiana
T
Domratcheva
1] Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 N. Mathews Ave, Urbana Illinois 61801, USA [2] Department of Physics, University of Illinois at Urbana-Champaign, 1110 W. Green Street, Urbana, Illinois 61801, USA.
Klaus
K
Schulten
D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D020134:Catalytic Domain; D056931:Cryptochromes / Q000737:chemistry* / Q000378:metabolism; D004579:Electron Transport; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry / Q000378:metabolism; D005609:Free Radicals / Q000737:chemistry* / Q000378:metabolism; D008027:Light; D060526:Magnetic Fields; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D011789:Quantum Theory; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism
D056931:Cryptochromes; D005609:Free Radicals; D005182:Flavin-Adenine Dinucleotide; D014364:Tryptophan