The Major Outer Membrane Protein of Chlamydia psittaci Functions as a Porin-Like Ion Channel

We report direct evidence for porin function obtained by using native, oligomeric major outer membrane protein incorporated into planar lipid bilayers

Susan Wyllie


Scholarcy highlights

  • The major outer membrane protein of Chlamydia species shares several biochemical properties with classical porin proteins
  • Western blots probed with monoclonal antibody specific for the oligomeric and monomeric forms of MOMP demonstrated that when MOMP is solubilized in sodium dodecyl sulfate sample buffer at room temperature in the presence of a reducing agent, it migrates with an apparent molecular mass of 100 kDa, which we interpret to represent an oligomer
  • MOMP remains the primary candidate for a chlamydial vaccine
  • Structural analysis by circular dichroism indicated that the secondary structure of MOMP was mainly ␤ sheet, similar to the high ␤-sheet content of bacterial porins previously characterized by X-ray crystallography
  • The modification of channel amplitude and open/closed transitions by the neutralizing MOMP-specific MAb A11 was of particular significance, for it confirmed that MOMP was the channel-forming protein and reinforced our belief that MOMP is arranged as an oligomer in the bilayer, since A11 recognizes only oligomeric MOMP upon Western blotting
  • This posed the question, What is the minimal conducting unit of the MOMP channel? From the results summarized in Fig. 6, we suggest that each MOMP molecule inserts into the bilayer as a trimer to give rise to three pores through the membrane, and that switching to holding potentials of Ϯ60 mV and above promotes the opening of all three pores together
  • We have recently reconstituted a recombinant major outer membrane protein into the planar lipid bilayer resulting in the formation of ion channels with properties identical to those of the native protein

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