Peptide-lipid interactions of the stress-response peptide TisB that induces bacterial persistence.
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.
Institute of Physical Chemistry, Karlsruhe Institute of Technology, Karlsruhe, Germany.
Thomas
T
Steinbrecher
Sebastian
S
Prock
Johannes
J
Reichert
Parvesh
P
Wadhwani
Benjamin
B
Zimpfer
Jochen
J
Bürck
Marina
M
Berditsch
Marcus
M
Elstner
Anne S
AS
Ulrich
D000595:Amino Acid Sequence; D001427:Bacterial Toxins / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000166:cytology* / Q000378:metabolism / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D016062:Porosity; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D013312:Stress, Physiological; D013816:Thermodynamics; D053835:Unilamellar Liposomes / Q000737:chemistry / Q000378:metabolism
D001427:Bacterial Toxins; D029968:Escherichia coli Proteins; D008051:Lipid Bilayers; D010446:Peptide Fragments; C575529:TisB toxin, E coli; D053835:Unilamellar Liposomes