title: The membrane insertion of helical antimicrobial peptides from the N-terminus of Helicobacter pylori ribosomal protein L1.
abstract: The interaction of two helical antimicrobial peptides, HPA3 and HPA3P with planar supported lipid membranes was quantitatively analysed using two complementary optical biosensors. The peptides are analogues of Hp(2-20) derived from the N-terminus of Helicobacter pylori ribosomal protein L1 (RpL1). The binding of these two peptide analogues to zwitterionic dimyristoyl-phosphatidylcholine (DMPC) and negatively charged membranes composed of DMPC/dimyristoylphosphatidylglycerol (DMPG) (4:1) was determined using surface plasmon resonance (SPR) and dual polarisation interferometry (DPI). Using SPR analysis, it was shown that the proline substitution in HPA3P resulted in much lower binding for both zwitterionic and anionic membranes than HPA3. Structural changes in the planar DMPC and DMPC/DMPG (4:1) bilayers induced by the binding of both Hp(2-20) analogues were then resolved in real-time with DPI. The overall process of peptide-induced changes in membrane structure was analysed by the real-time changes in bound peptide mass as a function of bilayer birefringence. The insertion of both HPA3 and HPA3P into the supported lipid bilayers resulted in a decrease in birefringence with increasing amounts of bound peptide which reflects a decrease in the order of the bilayer. The binding of HPA3 to each membrane was associated with a higher level of bound peptide and greater membrane lipid disordering and a faster and higher degree of insertion into the membrane than HPA3P. Furthermore, the binding of both HPA3 and HPA3P to negatively charged DMPC/DMPG bilayers also leads to a greater disruption of the lipid ordering. These results demonstrate the geometrical changes in the membrane upon peptide insertion and the extent of membrane structural changes can be obtained quantitatively. Moreover, monitoring the effect of peptides on a structurally characterised bilayer has provided further insight into the role of membrane structure changes in the molecular basis of peptide selectivity and activity and may assist in defining the mode of antimicrobial action.
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Wellington Rd, Clayton, Vic, 3800, Australia.
authors.forename: Tzong-Hsien
authors.initials: TH
authors.lastname: Lee
authors.forename: Kristopher N
authors.initials: KN
authors.lastname: Hall
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Swann
authors.forename: Jonathan F
authors.initials: JF
authors.lastname: Popplewell
authors.forename: Sharon
authors.initials: S
authors.lastname: Unabia
authors.forename: Yoonkyung
authors.initials: Y
authors.lastname: Park
authors.forename: Kyung-Soo
authors.initials: KS
authors.lastname: Hahm
authors.forename: Marie-Isabel
authors.initials: MI
authors.lastname: Aguilar
mesh_terms: D000595:Amino Acid Sequence; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry / Q000378:metabolism*; D001718:Birefringence; D002942:Circular Dichroism; D004560:Electricity; D016480:Helicobacter pylori / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008280:Magnetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D008970:Molecular Weight; D044367:Phase Transition; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012269:Ribosomal Proteins / Q000737:chemistry* / Q000378:metabolism*; D020349:Surface Plasmon Resonance; D013696:Temperature
chemical_list: D023181:Antimicrobial Cationic Peptides; D008051:Lipid Bilayers; D012269:Ribosomal Proteins; C028546:ribosomal protein L1