Kim, Hanseong; Zou, Taisong; Modi, Chintan; Doerner, Katerina; Grunkemeyer, Timothy J.; Chen, Liqing; Fromme, Raimund; Matz, Mikhail V.; Ozkan, S. Banu; Wachter, Rebekka M.
A Hinge Migration Mechanism Unlocks the Evolution of Green-to-Red Photoconversion in GFP-like Proteins
STRUCTURE, 23:34-43, JAN 6 2015

In proteins, functional divergence involves mutations that modify structure and dynamics. Here we provide experimental evidence for an evolutionary mechanism driven solely by long-range dynamic motions without significant backbone adjustments, catalytic group rearrangements, or changes in subunit assembly. Crystallographic structures were determined for several reconstructed ancestral proteins belonging to a GFP class frequently employed in superresolution microscopy. Their chain flexibility was analyzed using moleculardynamics and perturbation response scanning. The green-to-red photoconvertible phenotype appears to have arisen from a common green ancestor by migration of a knob-like anchoring region away from the active site diagonally across the beta barrel fold. The allosterically coupled mutational sites provide active site conformational mobility via epistasis. We propose that light-induced chromophore twisting is enhanced in a reverse-protonated subpopulation, activating internal acid-base chemistry and backbone cleavage to enlarge the chromophore. Dynamics-driven hinge migration may represent a more general platform for the evolution of novel enzyme activities.

DOI:10.1016/j.str.2014.11.011

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