biostudies-literatureHan CTNational Institutes of HealthUniversity of California Santa Barbara Institute for Collaborative BiotechnologiesNIGMS NIH HHSNational Science FoundationWest Virginia University168-179https://www.ebi.ac.uk/biostudies/studies/S-EPMC9822798biostudies-literatureUnknown122(1)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<sub>D97</subBiophysical journalLipid membrane mimetics and oligomerization tune functional properties of proteorhodopsin.PMC9822798R35 GM136411Nguyen KDQO'Malley MAChmelka BFWinslow ERahman MHan SBerkow MWMertz BKiani AHussain SBaxter NKinnebrew MIdso MNChang EHan CTAye ESeppala SfalseLipid membrane mimetics and oligomerization tune functional properties of proteorhodopsin.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<sub>D97</sub2023-01-01T00:00:00Z2023 Jan2026-05-28T02:09:50.964Z2025-04-04T03:20:35.981ZS-EPMC98227983635278410.1016/j.bpj.2022.11.012