Peptide-Lipid Interactions of the Stress-Response Peptide TisB That Induces Bacterial Persistence

• Published in: Biophysical journal Vol. 103; no. 7; pp. 1460 - 1469
• Main Authors: Steinbrecher, Thomas, Prock, Sebastian, Reichert, Johannes, Wadhwani, Parvesh, Zimpfer, Benjamin, Bürck, Jochen, Berditsch, Marina, Elstner, Marcus, Ulrich, Anne S.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 03.10.2012; Biophysical Society; The Biophysical Society
• Subjects: adenosine triphosphate; Amino Acid Sequence; Bacterial Toxins - chemistry; Bacterial Toxins - metabolism; biofilm; Biofilms; Cell Membrane - chemistry; Cell Membrane - metabolism; E coli; Escherichia coli; Escherichia coli - cytology; Escherichia coli - metabolism; Escherichia coli - physiology; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - metabolism; hydrophobicity; Lipid Bilayers - chemistry; Lipid Bilayers - metabolism; Lipids; Membrane; membrane potential; Membranes; molecular dynamics; Molecular Dynamics Simulation; Molecular Sequence Data; Molecules; Peptide Fragments - chemistry; Peptide Fragments - metabolism; Peptides; Porosity; Protein Binding; Protein Multimerization; Protein Structure, Quaternary; protons; Simulation; stress response; Stress, Physiological; Thermodynamics; Unilamellar Liposomes - chemistry; Unilamellar Liposomes - metabolism
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1016/j.bpj.2012.07.060

The bacterial stress-response peptide TisB in Escherichia coli has been suggested to dissipate the transmembrane potential, such that the depletion of ATP levels induces the formation of dormant persister cells which can eventually form biofilms. We studied the structure and membrane interactions of TisB to find out whether it forms pores or other proton-selective channels. Circular dichroism revealed an amphiphilic α-helical structure when reconstituted in lipid vesicles, and oriented circular dichroism showed that the helix assumes a transmembrane alignment. The addition of TisB to dye-loaded vesicles caused leakage only at very high peptide concentration, notably with a Hill coefficient of 2, which suggests that dimers must be involved. Coarse-grained molecular dynamics simulations showed that membrane binding of monomeric TisB is rapid and spontaneous, and transmembrane insertion is energetically feasible. When TisB oligomers are assembled as transmembrane pores, these channels collapse during the simulations, but transmembrane dimers are found to be stable. Given the pattern of charges on the amphiphilic TisB helix, we postulate that antiparallel dimers could be assembled via a ladder of salt bridges. This electrostatic charge-zipper could enable protons to pass along a wire of trapped water molecules across the hydrophobic membrane.