Verchère, Alice; Ou, Wei-Lin; Ploier, Birgit; Morizumi, Takefumi; Goren, Michael A; Bütikofer, Peter; Ernst, Oliver P; Khelashvili, George; Menon, Anant K (2017). Light-independent phospholipid scramblase activity of bacteriorhodopsin from Halobacterium salinarum. Scientific Reports, 7(1), p. 9522. Nature Publishing Group 10.1038/s41598-017-09835-5
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The retinylidene protein bacteriorhodopsin (BR) is a heptahelical light-dependent proton pump found in the purple membrane of the archaeon Halobacterium salinarum. We now show that when reconstituted into large unilamellar vesicles, purified BR trimers exhibit light-independent lipid scramblase activity, thereby facilitating transbilayer exchange of phospholipids between the leaflets of the vesicle membrane at a rate >10,000 per trimer per second. This activity is comparable to that of recently described scramblases including bovine rhodopsin and fungal TMEM16 proteins. Specificity tests reveal that BR scrambles fluorescent analogues of common phospholipids but does not transport a glycosylated diphosphate isoprenoid lipid. In silico analyses suggest that membrane-exposed polar residues in transmembrane helices 1 and 2 of BR may provide the molecular basis for lipid translocation by coordinating the polar head-groups of transiting phospholipids. Consistent with this possibility, extensive coarse-grained molecular dynamics simulations of a BR trimer in an explicit phospholipid membrane revealed water penetration along transmembrane helix 1 with the cooperation of a polar residue (Y147 in transmembrane helix 5) in the adjacent protomer. These results suggest that the lipid translocation pathway may lie at or near the interface of the protomers of a BR trimer.
Item Type: |
Journal Article (Original Article) |
|---|---|
Division/Institute: |
04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Biochemistry and Molecular Medicine |
UniBE Contributor: |
Bütikofer, Peter |
Subjects: |
500 Science > 570 Life sciences; biology 600 Technology > 610 Medicine & health |
ISSN: |
2045-2322 |
Publisher: |
Nature Publishing Group |
Language: |
English |
Submitter: |
Barbara Franziska Järmann-Bangerter |
Date Deposited: |
01 Mar 2018 14:24 |
Last Modified: |
05 Dec 2022 15:10 |
Publisher DOI: |
10.1038/s41598-017-09835-5 |
PubMed ID: |
28842688 |
BORIS DOI: |
10.7892/boris.110068 |
URI: |
https://boris.unibe.ch/id/eprint/110068 |
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