Glutamine Amide Flip Elicits Long Distance Allosteric Responses in the LOV Protein Vivid.
Light-oxygen-voltage (LOV) domains sense blue light through the photochemical formation of a cysteinyl-flavin covalent adduct. Concurrent protonation at the flavin N5 position alters the hydrogen bonding interactions of an invariant Gln residue that has been proposed to flip its amide side chain as a critical step in the propagation of conformational change. Traditional molecular dynamics (MD) and replica-exchange MD (REMD) simulations of the well-characterized LOV protein Vivid (VVD) demonstrate that the Gln182 amide indeed reorients by ∼180° in response to either adduct formation or reduction of the isoalloxazine ring to the neutral semiquinone, both of which involve N5 protonation. Free energy simulations reveal that the relative free energies of the flipped Gln conformation and the flipping barrier are significantly lower in the light-adapted state. The Gln182 flip stabilizes an important hinge-bβ region between the PAS β-sheet and the N-terminal cap helix that in turn destabilizes an N-terminal latch region against the PAS core. Release of the latch, observed both experimentally and in the simulations, is known to mediate light-induced VVD dimerization. This computational study of a LOV protein, unprecedented in its agreement with experiment, provides an atomistic view of long-range allosteric coupling in a photoreceptor.
Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 45470 Mülheim an der Ruhr, Germany.
Abir
A
Ganguly
Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 45470 Mülheim an der Ruhr, Germany.
Walter
0000-0001-6780-0350
W
Thiel
Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853, United States.
Brian R
0000-0001-8234-9991
BR
Crane
D000494:Allosteric Regulation; D000577:Amides / Q000737:chemistry / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D005973:Glutamine / Q000737:chemistry / Q000378:metabolism*; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D013816:Thermodynamics
D000577:Amides; D005656:Fungal Proteins; C423283:VVD protein, Neurospora crassa; D005973:Glutamine