Pore forming activity of the major outer membrane protein ofRhodobacter capsulatusin lipid bilayer membranes

✍ Scribed by R. Benz; D. Woitzik; H. T. Flammann; J. Weckesser

• Publisher: Springer
• Year: 1987
• Tongue: English
• Weight: 532 KB
• Volume: 148
• Category: Article
• ISSN: 0302-8933
• DOI: 10.1007/bf00414816

✦ Synopsis

Porin of the outer membrane of Rhodobacter capsulatus St. Louis (ATCC 23782) was isolated and reconstituted into lipid bilayer membranes. The porin was obtained either by the sodium dodecyl sulfate treatment of cell envelopes (SDS-porin) or by saline extraction of whole cells (NaCl-porin). Nanomolar concentrations of both porin preparations resulted in a strong conductance increase of the lipid bilayer membranes by many orders of magnitude. At small protein concentrations the conductance increased in a stepwise fashion, the average single channel conductance being about 0.35 nS in 0.1 M KC1 for SDS-porin and NaC1porin as well. The single channel conductance was a linear function of the specific conductance of the aqueous phase. The results were consistent with the assumption that the porin formed large water-filled transmembrane channels in the membrane. From the average value of the single channel 9 conductance in 0.1 M KC1 an effective channel diameter of about 1.5 nm was estimated for both types of porins.