CpHMD-Then-QM/MM Identification of the Amino Acids Responsible for the Anabaena Sensory Rhodopsin pH-Dependent Electronic Absorption Spectrum

Elisa Pieri (1) , Vincent Ledentu (1) , Michael Sahlin (1) , François Dehez (2) , Massimo Olivucci (3, 4) , Nicolas Ferré (1)

1 ICR - Institut de Chimie Radicalaire
2 LPCT - Laboratoire de Physique et Chimie Théoriques
3 Dipartimento di Chimica
4 BGSU - Bowling Green State University

Anabaena Sensory Rhodopsin (ASR), a microbial photoactive protein featuring the retinal chromophore in two different conformations, exhibits a pH-dependent electronic absorption spectrum. Using the recently developed CpHMD-then-QM/MM multiscale protocol applied to ASR embedded in a membrane model, the pH-induced changes in its maximum absorption wavelength have been reproduced and analyzed. While the acidic 1 tiny red-shift is essentially correlated with the deprotonation of an aspartic acid located on the ASR extracellular side, the larger blue-shift experimentally reported at pH values larger than 5 involves a cluster of titrating residues sitting on the cytoplasmic side. The ASR pH-dependent spectrum is the consequence of the competitive stabilization of retinal ground and excited states by the protein electrostatic potential.

Domaines: Chimie théorique et/ou physique

Elisa Pieri, Vincent Ledentu, Michael Sahlin, François Dehez, Massimo Olivucci, et al.. CpHMD-Then-QM/MM Identification of the Amino Acids Responsible for the Anabaena Sensory Rhodopsin pH-Dependent Electronic Absorption Spectrum. Journal of Chemical Theory and Computation, 2019, 15 (8), pp.4535-4546. ⟨10.1021/acs.jctc.9b00221⟩. ⟨hal-02171700⟩