title: Physicochemical Studies on Orientation and Conformation of a New Bacteriocin BacSp222 in a Planar Phospholipid Bilayer.
abstract: The behavior, secondary structure, and orientation of a recently discovered bacteriocin-like peptide BacSp222 in a lipid model system supported at a gold electrode was investigated by chronocoulometry, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and attenuated total reflectance infrared (ATR-IR) spectroscopy. The IR spectra show that the secondary structure of BacSp222 is predominantly α-helical. Analysis of the spectra in the amide I region shows that the α-helical fragment of the peptide is inserted into bilayer at the potential range at which the bilayer is stable and attached to the Au(111) surface, i.e., from -0.5 to 0.3 V vs Ag/AgCl. Insertion of BacSp222 to the membrane significantly changes the conformation of the acyl chains of lipid molecules, from all-trans to partially melted; however, the chains become less tilted. Based on these results, we propose that BacSp222 interacts with the DMPC bilayer through the barrel-stave pore formation. In this model, α-helix of BacSp222 inserts into the membrane with an angle between the α-helix axis and membrane normal equal to ∼18°. The changes in orientation of the α-helical fragment of the peptide indicate that the orientation of BacSp222 with respect to the bilayer surface is potential-dependent. The peptide is inserted into the membrane driven by the electrostatic field generated by negative charge at the metal surface. It is not inserted at negative potentials where the membrane is detached from the metal and no longer exposed to the electrostatic field of the metal.
authors.affiliation: Institute of Physical Chemistry Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Pieta
authors.affiliation: Institute of Physical Chemistry Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Marta
authors.initials: M
authors.lastname: Majewska
authors.forename: Zhangfei
authors.initials: Z
authors.lastname: Su
authors.forename: Michael
authors.initials: M
authors.lastname: Grossutti
authors.affiliation: Department of Analytical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University , Gronostajowa 7, 30-387 Krakow, Poland.
authors.forename: Benedykt
authors.initials: B
authors.lastname: Wladyka
authors.affiliation: Department of Analytical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University , Gronostajowa 7, 30-387 Krakow, Poland.|3rd Department of General Surgery, Jagiellonian University Medical College , Pradnicka 35-37, 31-008 Krakow, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Piejko
authors.forename: Jacek
authors.initials: J
authors.lastname: Lipkowski
authors.affiliation: Department of Analytical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University , Gronostajowa 7, 30-387 Krakow, Poland.
authors.forename: Pawel
authors.initials: P
authors.lastname: Mak
mesh_terms: D001430:Bacteriocins / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D001430:Bacteriocins; D008051:Lipid Bilayers; D010743:Phospholipids