FEBS Letters
Volume 581, Issue 5 , Pages 804-808, 6 March 2007

Asymmetry of syringomycin E channel studied by polymer partitioning

Edited by Maurice Montal

  • Olga S. Ostroumova

      Affiliations

    • Institute of Cytology of the Russian Academy of Sciences, St. Petersburg, 194064, Russia
    • ,
  • Philip A. Gurnev

      Affiliations

    • National Institute of Child Health and Human Development, NIH, 9000 Rockville Pk., Bldg. 9, Rm. 1N-124B, Bethesda, MD 20892-0924, USA
    • ,
  • Ludmila V. Schagina

      Affiliations

    • Institute of Cytology of the Russian Academy of Sciences, St. Petersburg, 194064, Russia
    • ,
  • Sergey M. Bezrukov

      Affiliations

    • National Institute of Child Health and Human Development, NIH, 9000 Rockville Pk., Bldg. 9, Rm. 1N-124B, Bethesda, MD 20892-0924, USA
    • Corresponding Author InformationCorresponding author. Fax: +1 301 496 2172.

Received 4 December 2006; received in revised form 22 January 2007; accepted 24 January 2007. published online 01 February 2007.

Abstract 

To probe the size of the ion channel formed by Pseudomonas syringae lipodepsipeptide syringomycin E, we use the partial blockage of ion current by penetrating poly(ethylene glycol)s. Earlier experiments with symmetric application of these polymers yielded a radius estimate of ∼1nm. Now, motivated by the asymmetric non-ohmic current–voltage curves reported for this channel, we explore its structural asymmetry. We gauge this asymmetry by studying the channel conductance after one-sided addition of differently sized poly(ethylene glycol)s. We find that small polymers added to the cis-side of the membrane (the side of lipodepsipeptide addition) reduce channel conductance much less than do the same polymers added to the trans-side. We interpret our results to suggest that the water-filled pore of the channel is conical with cis- and trans-radii differing by a factor of 2–3 and that the smaller cis-radius is in the 0.25–0.35nm range. In symmetric, two-sided addition, polymers entering the pore from the larger opening dominate blockage.

Abbreviations: SRE, syringomycin E, PEG, poly(ethylene glycol), PS, 1,2-dioleoyl-sn-glycero-3-phosphoserine, PE, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine

Keywords: Syringomycin E, Channel sizing, Polymer exclusion, Lipid bilayers, Poly(ethylene glycol)s

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PII: S0014-5793(07)00092-0

doi:10.1016/j.febslet.2007.01.063

FEBS Letters
Volume 581, Issue 5 , Pages 804-808, 6 March 2007

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