Lipid membrane mimetics and oligomerization tune functional properties of proteorhodopsin.

Autor:	Han CT; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California., Nguyen KDQ; Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California., Berkow MW; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California., Hussain S; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California., Kiani A; C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia., Kinnebrew M; College of Creative Studies, Biology Department, University of California, Santa Barbara, Santa Barbara, California., Idso MN; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California., Baxter N; Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California., Chang E; Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California., Aye E; Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California., Winslow E; Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California., Rahman M; C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia., Seppälä S; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California., O'Malley MA; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California., Chmelka BF; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California., Mertz B; C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia., Han S; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California; Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California. Electronic address: songi@chem.ucsb.edu.
Jazyk:	angličtina
Zdroj:	Biophysical journal [Biophys J] 2023 Jan 03; Vol. 122 (1), pp. 168-179. Date of Electronic Publication: 2022 Nov 09.
DOI:	10.1016/j.bpj.2022.11.012
Abstrakt:	The functional properties of proteorhodopsin (PR) have been found to be strongly modulated by oligomeric distributions and lipid membrane mimetics. This study aims to distinguish and explain their effects by investigating how oligomer formation impacts PR's function of proton transport in lipid-based membrane mimetic environments. We find that PR forms stable hexamers and pentamers in both E. coli membranes and synthetic liposomes. Compared with the monomers, the photocycle kinetics of PR oligomers is ∼2 and ∼4.5 times slower for transitions between the K and M and the M and N photointermediates, respectively, indicating that oligomerization significantly slows PR's rate of proton transport in liposomes. In contrast, the apparent pKa of the key proton acceptor residue D97 (pKa D97 ) of liposome-embedded PR persists at 6.2-6.6, regardless of cross-protomer modulation of D97, suggesting that the liposome environment helps maintain PR's functional activity at neutral pH. By comparison, when extracted directly from E. coli membranes into styrene-maleic acid lipid particles, the pKa D97 of monomer-enriched E50Q PR drastically increases to 8.9, implying that there is a very low active PR population at neutral pH to engage in PR's photocycle. These findings demonstrate that oligomerization impacts PR's photocycle kinetics, while lipid-based membrane mimetics strongly affect PR's active population via different mechanisms. Competing Interests: Declaration of interests The authors declare no competing interests. (Copyright © 2022 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
Databáze:	MEDLINE
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