Escherichia coli phage-shock protein A (PspA) binds to membrane phospholipids and repairs proton leakage of the damaged membranes

Authors

  • Ryuji Kobayashi,

    1. Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8503, Japan.
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  • Toshiharu Suzuki,

    1. International Cooperative Research Project (ICORP), Japan Science and Technology Corporation (JST), Aoumi 2-41, Tokyo 135-0064, Japan.
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  • Masasuke Yoshida

    Corresponding author
    1. Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8503, Japan.
    2. International Cooperative Research Project (ICORP), Japan Science and Technology Corporation (JST), Aoumi 2-41, Tokyo 135-0064, Japan.
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*E-mail myoshida@res.titech.ac.jp; Tel. (+81) 45 924 5233; Fax (+81) 45 924 5277.

Summary

Escherichia coli phage-shock protein A (PspA), a 25.3 kDa peripheral membrane protein, is induced under the membrane stress conditions and is assumed to help maintain membrane potential. Here, we report that purified PspA, existing as a large oligomer, is really able to suppress proton leakage of the membranes. This was demonstrated for membrane vesicles prepared from the PspA-lacking E. coli mutants, and for membrane vesicles damaged by ethanol and Triton X-100 prepared from the mutant and the wild-type cells. PspA also suppressed proton leakage of damaged liposomes made from E. coli total lipids. Furthermore, we found that PspA bound preferentially to liposomes containing phosphatidylserine and phosphatidylglycerol. All these effects were not observed for monomer PspA that was prepared by refolding of urea-denatured PspA. These results indicate that oligomers of PspA bind to membrane phospholipids and suppress proton leakage.

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