Functional characterization of pediocin PA-1 binding to liposomes in the absence of a protein receptor and its relationship to a predicted tertiary structure.
The physicochemical interaction of pediocin PA-1 with target membranes was characterized using lipid vesicles made from the total lipids extracted from Listeria monocytogenes. Pediocin PA-1 caused the time- and concentration-dependent release of entrapped carboxyfluorescein (CF) from the vesicles. The pediocin-induced CF efflux rates were higher under acidic conditions than under neutral and alkaline conditions and were dependent on both pediocin and lipid concentrations. A binding isotherm constructed on the basis of the Langmuir isotherm gave an apparent binding constant of 1.4 x 10(7) M-1 at pH 6.0. The imposition of a transmembrane potential (inside negative) increased the CF efflux rate by 88%. Pediocin PA-1 also permeablized synthetic vesicles composed only of phosphatidylcholine. Sequence alignments and secondary-structure predictions for the N terminus of pediocin PA-1 and other class IIa bacteriocins predicted that pediocin PA-1 contained two beta-sheets maintained in a hairpin conformation stabilized by a disulfide bridge. The structural model also revealed patches of positively charged residues, consistent with the argument that electrostatic interactions play an important role in the binding of pediocin PA-1 to the lipid vesicles. This study demonstrates that pediocin PA-1 can function in the absence of a protein receptor and provides a structural model consistent with these results.
Chen
Y
Y
Department of Food Science, New Jersey Agricultural Experiment Station, Cook College, Rutgers, State University of New Jersey, New Brunswick 08903-0231, USA.
Shapira
R
R
Eisenstein
M
M
Montville
T J
TJ
D000595:Amino Acid Sequence; D001430:Bacteriocins / Q000737:chemistry* / Q000378:metabolism*; D001692:Biological Transport; D003198:Computer Simulation; D005452:Fluoresceins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008081:Liposomes / Q000378:metabolism*; D008564:Membrane Potentials; D008958:Models, Molecular; D008969:Molecular Sequence Data; D000070017:Pediocins; D010539:Permeability; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
D001430:Bacteriocins; D005452:Fluoresceins; D008081:Liposomes; D000070017:Pediocins; C074288:pediocin PA-1; C024098:6-carboxyfluorescein