Deciphering the Spectral Tuning Mechanism in Proteorhodopsin: The Dominant Role of Electrostatics Instead of Chromophore Geometry

Jonathan Church, Gil S. Amoyal, Veniamin A. Borin, Suliman Adam, Jógvan Magnus Haugaard Olsen, Igor Schapiro*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Proteorhodopsin (PR) is a photoactive proton pump found in marine bacteria. There are two phenotypes of PR exhibiting an environmental adaptation to the ocean’s depth which tunes their maximium absorption: blue-absorbing proteorhodopsin (BPR) and green-absorbing proteorhodopsin (GPR). This blue/green color-shift is controlled by a glutamine to leucine substitution at position 105 which accounts for a 20 nm shift. Typically, spectral tuning in rhodopsins is rationalized by the external point charge model but the Q105L mutation is charge neutral. To study this tuning mechanism we employed the hybrid QM/MM method with sampling from molecular dynamics. Our results reveal that the positive partial charge of glutamine near the C14–C15 bond of retinal shortens the effective conjugation length of the chromophore compared to the leucine residue. The derived mechanism can be applied to explain the color regulation in other retinal proteins and can serve as a guideline for rational design of spectral shifts.
Original languageEnglish
Article numbere202200139
JournalChemistry: A European Journal
Volume28
Issue number28
Number of pages8
ISSN0947-6539
DOIs
Publication statusPublished - 2022

Keywords

  • Rhodopsin
  • Proteorhodopsin
  • Retinal
  • Spectral Tuning
  • QM/MM

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