Channel-forming activity of syringopeptin 25A in mercury-supported phospholipid monolayers and negatively charged bilayers.
Interactions of the cationic lipodepsipeptide syringopeptin 25A (SP25A) with mercury-supported dioleoylphosphatidylcholine (DOPC), dioleoylphosphatidylserine (DOPS) and dioeleoylphosphatidic acid (DOPA) self-assembled monolayers (SAMs) were investigated by AC voltammetry in 0.1M KCl at pH3, 5.4 and 6.8. SP25A targets and penetrates the DOPS SAM much more effectively than the other SAMs not only at pH6.8, where the DOPS SAM is negatively charged, but also at pH3, where it is positively charged just as SP25A. Similar investigations at tethered bilayer lipid membranes (tBLMs) consisting of a thiolipid called DPTL anchored to mercury, with a DOPS, DOPA or DOPC distal monolayer on top of it, showed that, at physiological transmembrane potentials, SP25A forms ion channels spanning the tBLM only if DOPS is the distal monolayer. The distinguishing chemical feature of the DOPS SAM is the ionic interaction between the protonated amino group of a DOPS molecule and the carboxylate group of an adjacent phospholipid molecule. Under the reasonable assumption that SP25A preferentially interacts with this ion pair, the selective lipodepsipeptide antimicrobial activity against Gram-positive bacteria may be tentatively explained by its affinity for similar protonated amino-carboxylate pairs, which are expected to be present in the peptide moieties of peptidoglycan strands.
Department of Chemistry, Florence University, via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy; Department of Chemistry, University of Padova, Via Marzolo 1, 35131 Padova, Italy. Electronic address: luci_be@tiscali.it.
Lucia
L
Becucci
Department of Chemistry, Florence University, via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy.
Arianna
A
Toppi
Department of Agricultural and Food Science, University of Naples "Federico II", 80055 Portici, Italy; School of Science, Engineering & Technology, Division of Food & Life Sciences, Abertay University, Kydd Building, Dundee DD1 1HG, UK.
Alberto
A
Fiore
Proteomics & Mass Spectrometry Laboratory, ISPAAM-National Research Council, 80147, Naples, Italy.
Andrea
A
Scaloni
Department of Chemistry, Florence University, via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy.
Rolando
R
Guidelli
D002021:Buffers; D004563:Electrochemistry; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism*; D008628:Mercury / Q000737:chemistry*; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000378:metabolism*; D010743:Phospholipids / Q000737:chemistry* / Q000378:metabolism*
D002021:Buffers; D008051:Lipid Bilayers; D010456:Peptides, Cyclic; D010743:Phospholipids; C098017:syringopeptin 25-A; D008628:Mercury
Antimicrobial peptides; Cyclic voltammetry; Ion channels; Lipid monolayers self-assembled on mercury; Lipodepsipeptides; Tethered bilayer lipid membranes