Comparison of functionality and structural stability of bacteriorhodopsin reconstituted in partially fluorinated dimyristoylphosphatidylcholine liposomes with different perfluoroalkyl chain lengths
Successful reconstitution of bR into liposomes of a series of partially fluorinated DMPCs with varied perfluoroalkyl lengths.
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Regardless of the perfluoroalkyl lengths, native-like structural and functional properties of reconstituted bR at 30 °C.
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Significant perfluoroalkyl chain length-dependent thermal stability of bR molecules and trimeric aggregate.
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High thermal stability of bR in the perfluorohexyl group-containing DMPC liposome comparable to the purple native membrane.
Abstract
Amphiphilic molecules with one or more perfluoroalkyl groups (Rf, CnF2n+1), which show peculiar interfacial properties, are attracting much attention in membrane protein science. We recently have developed a partially fluorinated dimyristoylphosphatidylcholine (DMPC) with a perfluorobutyl group in the hydrophobic chain terminal (F4-DMPC) and demonstrated that F4-DMPC is a promising material for incorporating membrane proteins. Moreover, we have found out that membrane properties of a series of partially fluorinated DMPCs with different Rf chain lengths (Fn-DMPCs) vary in a significant Rf chain length-dependent manner. In the present study, structural and functional properties of a membrane protein bacteriorhodopsin (bR) in the Fn-DMPC (n = 4, 6, and 8) membranes (bR/Fn-DMPC) are investigated using several physicochemical techniques. Regardless of the Rf chain lengths, bR/Fn-DMPCs retain native-like structural and functional properties at 30 °C, unlike bR molecules in DMPC vesicles. In particular, bR/F6-DMPC, which is in the fluid phase at 30 °C, shows flash-induced transient absorption changes very similar to the native purple membrane (PM) and very high thermal stability of bR trimers comparable to the PM. Structural and functional properties of bR/Fn-DMPCs are discussed compared to the PM and bR/DMPC.
Graphical abstract
Abbreviations
bR
bacteriorhodopsin
CD
circular dichroism
DMPC
1,2-Dimyristoyl-sn-glycero-phosphocholine
DPPC
1,2-Dipalmitoyl-sn-glycero-phosphocholine
Fn-DMPC
partially fluorinated DMPC with varied perfluoroalkyl (CnF2n+1) chain lengths