Deciphering the Spectral Tuning Mechanism in Proteorhodopsin: The Dominant Role of Electrostatics Instead of Chromophore Geometry.
Chemistry
; 28(28): e202200139, 2022 May 16.
Article
in En
| MEDLINE
| ID: mdl-35307890
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 maximum 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 20â
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.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Rhodopsins, Microbial
/
Glutamine
Language:
En
Journal:
Chemistry
Journal subject:
QUIMICA
Year:
2022
Type:
Article
Affiliation country:
Israel