title: Gly(6) of kalata B1 is critical for the selective binding to phosphatidylethanolamine membranes.
abstract: The membrane interaction of the cyclotide kalata B1, an all-d-analogue and a single alanine substituted analogue (G6A), was studied by surface plasmon resonance (SPR) and atomic force microscopy (AFM). Kalata B1 showed a strong binding selectivity for dimyristoyl-phosphatidylethanolamine (DMPE) compared to dimyristoyl-phoshatidylcholine (DMPC)-containing lipids. However, when the interaction was visualized by AFM the peptide interacted with DMPC and DMPE in a similar manner. There was no apparent change in membrane morphology with either lipid, suggesting that kalata B1 does not act via a carpet-like disruption mechanism. The d-analogue showed similar binding by SPR and the same strong selectivity for DMPE, indicating that the membrane-interaction and lipid selectivity are not stereo-specific. SPR studies of the G6A analogue revealed that it interacted in a similar way to kalata B1 on the DMPC containing lipids, but showed no increased response on the DMPE containing lipids observed for kalata B1 and d-kalata B1. These results indicate that the Gly6 residue directly influences membrane binding as it is located near a putative membrane interacting hydrophobic patch. Overall, the data suggest that very small changes in amino acid composition (with no change in conformation) can influence specific self-association in combination with membrane binding and mediate the activity of kalata B1.
authors.affiliation: Department of Biochemistry & Molecular Biology, Monash University, Clayton, Australia.
authors.forename: Kristopher
authors.initials: K
authors.lastname: Hall
authors.forename: Tzong-Hsien
authors.initials: TH
authors.lastname: Lee
authors.forename: Norelle L
authors.initials: NL
authors.lastname: Daly
authors.forename: David J
authors.initials: DJ
authors.lastname: Craik
authors.forename: Marie-Isabel
authors.initials: MI
authors.lastname: Aguilar
mesh_terms: D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism; D002942:Circular Dichroism; D047169:Cyclotides / Q000737:chemistry*; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D008055:Lipids / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D008567:Membranes, Artificial; D018625:Microscopy, Atomic Force / Q000379:methods; D008969:Molecular Sequence Data; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D020349:Surface Plasmon Resonance; D013997:Time Factors
chemical_list: D047169:Cyclotides; D004220:Disulfides; D008055:Lipids; D008081:Liposomes; D008567:Membranes, Artificial; D010714:Phosphatidylethanolamines; C091930:kalata B1; C483858:phosphatidylethanolamine; D004134:Dimyristoylphosphatidylcholine; C018525:1,2-dimyristoylphosphatidylethanolamine