A role of complexin-lipid interactions in membrane fusion.
Complexins (Cpxs) and synaptotagmins regulate calcium-dependent exocytosis. A central helix in Cpx confers specific binding to the soluble N-ethylmaleimide-sensitive factor-attachment protein receptor (SNARE) fusion machinery. An accessory helix in the amino-terminal region inhibits membrane fusion by blocking SNAREpin zippering. We now show that an amphipathic helix in the carboxy-terminal region of CpxI binds lipid bilayers and affects SNARE-mediated lipid mixing in a liposome fusion assay. The substitution of a hydrophobic amino acid within the helix by a charged residue abolishes the lipid interaction and the stimulatory effect of CpxI in liposome fusion. In contrast, the introduction of the bulky hydrophobic amino acid tryptophan stimulates lipid binding and liposome fusion. This data shows that local Cpx-lipid interactions can play a role in membrane fusion.
Seiler
Florian
F
Heidelberg University Biochemistry Center, Im Neuenheimer Feld 345, 69120 Heidelberg, Germany.
Malsam
Jörg
J
Krause
Jean Michel
JM
Söllner
Thomas H
TH
D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000818:Animals; D006801:Humans; D008051:Lipid Bilayers / Q000378:metabolism*; D008055:Lipids / Q000737:chemistry*; D008081:Liposomes / Q000378:metabolism*; D008561:Membrane Fusion / Q000502:physiology*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D050600:SNARE Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D033942:Adaptor Proteins, Vesicular Transport; D008051:Lipid Bilayers; D008055:Lipids; D008081:Liposomes; D009419:Nerve Tissue Proteins; D050600:SNARE Proteins; C095992:complexin I; C095993:complexin II