Predicting Mutation-Induced Changes in the Electronic Properties of Photosynthetic Proteins from First Principles: The Fenna-Matthews-Olson Complex Example

Multiscale molecular modeling is utilized to predictoptical absorptionand circular dichroism spectra of two single-point mutants of theFenna-Matthews-Olson photosynthetic pigment-proteincomplex. The modeling approach combines classical molecular dynamicssimulations with structural refinement of photosynthetic pigmentsand calculations of their excited states in a polarizable proteinenvironment. The only experimental input to the modeling protocolis the X-ray structure of the wild-type protein. The first-principlesmodeling reproduces changes in the experimental optical spectra ofthe considered mutants, Y16F and Q198V. Interestingly, the Q198V mutationhas a negligible effect on the electronic properties of the targetedbacteriochlorophyll a pigment. Instead, the electronicproperties of several other pigments respond to this mutation. Themolecular modeling demonstrates that a single-point mutation can inducelong-range effects on the protein structure, while extensive structuralchanges near a pigment do not necessarily lead to significant changesin the electronic properties of that pigment.