title: Modulation of spectral properties and pump activity of proteorhodopsins by retinal analogues.
abstract: Proteorhodopsins are heptahelical membrane proteins which function as light-driven proton pumps. They use all-trans-retinal A1 as a ligand and chromophore and absorb visible light (520-540 nm). In the present paper, we describe modulation of the absorbance band of the proteorhodopsin from Monterey Bay SAR 86 gammaproteobacteria (PR), its red-shifted double mutant PR-D212N/F234S (PR-DNFS) and Gloeobacter rhodopsin (GR). This was approached using three analogues of all-trans-retinal A1, which differ in their electronic and conformational properties: all-trans-6,7-s-trans-locked retinal A1, all-trans-phenyl-retinal A1 and all-trans-retinal A2. We further probed the effect of these retinal analogues on the proton pump activity of the proteorhodopsins. Our results indicate that, whereas the constraints of the retinal-binding pocket differ for the proteorhodopsins, at least two of the retinal analogues are capable of shifting the absorbance bands of the pigments either bathochromically or hypsochromically, while maintaining their proton pump activity. Furthermore, the shifts implemented by the analogues add up to the shift induced by the double mutation in PR-DNFS. This type of chromophore substitution may present attractive applications in the field of optogenetics, towards increasing the flexibility of optogenetic tools or for membrane potential probes.
authors: *Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
authors: Srividya
authors: S
authors: Ganapathy
authors: *Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
authors: Odette
authors: O
authors: Bécheau
authors: ‡Centre for Molecular and Biomolecular Informatics, Radboud University Medical Center, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
authors: Hanka
authors: H
authors: Venselaar
authors: *Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
authors: Siebren
authors: S
authors: Frölich
authors: §Swammerdam Institute for Life Sciences, University of Amsterdam, P.O. Box 94215, 1090 GE Amsterdam, The Netherlands.
authors: Jeroen B
authors: JB
authors: van der Steen
authors: §Swammerdam Institute for Life Sciences, University of Amsterdam, P.O. Box 94215, 1090 GE Amsterdam, The Netherlands.
authors: Que
authors: Q
authors: Chen
authors: *Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
authors: Sarah
authors: S
authors: Radwan
authors: *Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
authors: Johan
authors: J
authors: Lugtenburg
authors: §Swammerdam Institute for Life Sciences, University of Amsterdam, P.O. Box 94215, 1090 GE Amsterdam, The Netherlands.
authors: Klaas J
authors: KJ
authors: Hellingwerf
authors: *Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
authors: Huub J M
authors: HJ
authors: de Groot
authors: *Department of Biophysical Organic Chemistry, Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
authors: Willem J
authors: WJ
authors: de Grip
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D000458:Cyanobacteria / Q000737:chemistry* / Q000235:genetics; D017494:Proton Pumps / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012172:Retinaldehyde / Q000031:analogs & derivatives / Q000737:chemistry; D012243:Rhodopsin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D025604:Rhodopsins, Microbial; D013056:Spectrophotometry, Ultraviolet
chemical_list: D001426:Bacterial Proteins; D017494:Proton Pumps; D025604:Rhodopsins, Microbial; C413548:proteorhodopsin; D012243:Rhodopsin; D012172:Retinaldehyde