Anionic lipids stimulate Sec-independent insertion of a membrane protein lacking charged amino acid side chains.
We have investigated the influence of the different lipid classes of Escherichia coli on Sec-independent membrane protein insertion, using an assay in which a mutant of the single-spanning Pf3 coat protein is biosynthetically inserted into liposomes. It was found that phosphatidylethanolamine and other non-bilayer lipids do not have a significant effect on insertion. Surprisingly, the anionic lipids phosphatidylglycerol and cardiolipin stimulate N-terminal translocation of the protein, even though it has no charged amino acid side chains. This novel effect is general for anionic lipids and depends on the amount of charge on the lipid headgroup. Since the N-terminus of the protein is at least partially positively charged due to a helix dipole moment, apparently negatively charged lipids can stimulate translocation of slightly positively charged protein segments in a direction opposite to the positive-inside rule. A mechanism is proposed to explain these results.
Ridder
A N
AN
Department of Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands. a.n.j.a.ridder@chem.uu.nl
Kuhn
A
A
Killian
J A
JA
de Kruijff
B
B
D000595:Amino Acid Sequence; D002213:Capsid / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D036022:Capsid Proteins; D002308:Cardiolipins / Q000737:chemistry / Q000494:pharmacology; D004926:Escherichia coli / Q000737:chemistry / Q000502:physiology*; D008051:Lipid Bilayers; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D010713:Phosphatidylcholines / Q000737:chemistry / Q000494:pharmacology; D010715:Phosphatidylglycerols / Q000737:chemistry / Q000494:pharmacology; D021381:Protein Transport
D036022:Capsid Proteins; D002308:Cardiolipins; D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; C051388:1,2-dioleoyl-sn-glycero-3-phosphoglycerol; C084332:major coat protein, Pseudomonas phage Pf3; C017251:1,2-oleoylphosphatidylcholine