title: The phase property of membrane phospholipids is affected by the functionality of signal peptides from the Escherichia coli ribose-binding protein.
abstract: We examined the effects of synthetic signal peptides from the wild-type, export-defective mutant and its revertant species of ribose-binding protein on the phase properties of lipid bilayers. The lateral segregation of phosphatidylglycerol (PG) in the lipid bilayer was detected through quenching between NBD-PGs upon the reconstitution of signal peptide into the liposome made with the Escherichia coli inner membrane composition. The tendency of lipid segregation was highly dependent on the export competency of signal peptides in vivo, with a decreasing order of wild-type, revertant, and mutant species. The colocalizations of pyrene-PG with BODIPY-PG were also induced by the signal peptides, confirming the phase separation of the acidic phospholipid. The wild-type and revertant signal peptides predominantly formed alpha-helical conformations with the presence of acidic phospholipid as determined by circular dichroism spectroscopy. In addition, they restricted the motion of lipid acyl chains as monitored by fluorescence anisotropy of DPH, suggesting a deep penetration of signal peptide into the lipid bilayer. However, the alpha-helical content of mutant signal peptide was only about half that of the wild-type or revertant peptide with a significantly smaller degree of penetration into the bilayer. An association of the defective signal peptides into the membrane was affected by salt extraction, whereas the functional ones were not. The aforementioned results indicate that the functionality of signal peptide is accomplished through its topologies in the membrane and also by its ability to induce lateral segregation of acidic phospholipid. We propose that the clustering of acidic phospholipid by the functional signal peptide is responsible for the formation of non-bilayer membrane structure, thereby promoting an efficient translocation of secretory proteins.
authors: Research Institute of Natural Science, Pai-Chai University, Taejon, 302-735 Korea.
authors: Taeho
authors: T
authors: Ahn
authors: Doo-Byoung
authors: DB
authors: Oh
authors: Hyoungman
authors: H
authors: Kim
authors: Chankyu
authors: C
authors: Park
mesh_terms: D001896:Boron Compounds; D002352:Carrier Proteins / Q000502:physiology*; D002942:Circular Dichroism; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D008051:Lipid Bilayers / Q000378:metabolism; D008563:Membrane Lipids / Q000502:physiology*; D033902:Periplasmic Binding Proteins; D010715:Phosphatidylglycerols / Q000378:metabolism; D010743:Phospholipids / Q000502:physiology*; D021382:Protein Sorting Signals / Q000502:physiology*; D017433:Protein Structure, Secondary
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; D008563:Membrane Lipids; D033902:Periplasmic Binding Proteins; D010715:Phosphatidylglycerols; D010743:Phospholipids; D021382:Protein Sorting Signals; C028003:RbsB protein, E coli