title: Investigating the interaction between peptides of the amphipathic helix of Hcf106 and the phospholipid bilayer by solid-state NMR spectroscopy.
abstract: The chloroplast twin arginine translocation (cpTat) system transports highly folded precursor proteins into the thylakoid lumen using the protonmotive force as its only energy source. Hcf106, as one of the core components of the cpTat system, is part of the precursor receptor complex and functions in the initial precursor-binding step. Hcf106 is predicted to contain a single amino terminal transmembrane domain followed by a Pro-Gly hinge, a predicted amphipathic α-helix (APH), and a loosely structured carboxy terminus. Hcf106 has been shown biochemically to insert spontaneously into thylakoid membranes. To better understand the membrane active capabilities of Hcf106, we used solid-state NMR spectroscopy to investigate those properties of the APH. In this study, synthesized peptides of the predicted Hcf106 APH (amino acids 28-65) were incorporated at increasing mol.% into 1-palmitoyl-2-oleoyl-sn-glycero-phosphocholine (POPC) and POPC/MGDG (monogalactosyldiacylglycerol; mole ratio 85:15) multilamellar vesicles (MLVs) to probe the peptide-lipid interaction. Solid-state (31)P NMR and (2)H NMR spectroscopic experiments revealed that the peptide perturbs the headgroup and the acyl chain regions of phospholipids as indicated by changes in spectral lineshape, chemical shift anisotropy (CSA) line width, and (2)H order SCD parameters. In addition, the comparison between POPC MLVs and POPC/MGDG MLVs indicated that the lipid bilayer composition affected peptide perturbation of the lipids, and such perturbation appeared to be more intense in a system more closely mimicking a thylakoid membrane.
authors.affiliation: Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Lishan
authors.initials: L
authors.lastname: Liu
authors.forename: Sergey
authors.initials: S
authors.lastname: Maltsev
authors.forename: Gary A
authors.initials: GA
authors.lastname: Lorigan
authors.forename: Carole
authors.initials: C
authors.lastname: Dabney-Smith
mesh_terms: D000595:Amino Acid Sequence; D038983:Galactolipids / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008565:Membrane Proteins / Q000737:chemistry*; D008954:Models, Biological; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020524:Thylakoids / Q000737:chemistry
chemical_list: D038983:Galactolipids; C109236:Hcf106 protein, plant; D008051:Lipid Bilayers; D008565:Membrane Proteins; D010455:Peptides; D010713:Phosphatidylcholines; D010940:Plant Proteins; C009909:monogalactosyldiacylglycerol; C028694:1-palmitoyl-2-oleoylphosphatidylcholine
keywords: 1-palmitoyl-2-oleoyl-sn-glycero-phosphocholine; APH; Amphipathic helix; CSA; Chloroplast TatB; MGDG; MLV; Membrane active peptide; POPC; S(CD); TMD; Twin arginine transport; amphipathic α-helix; chemical shift anisotropy; chloroplast twin arginine transport; cpTat; monogalactosyl diacylglycerol; multilamellar vesicles; segmental C–D bond order parameter; transmembrane domain