Single channel activity of OmpF-like porin from Yersinia pseudotuberculosis

Abstract

To gain a mechanistic insight in the functioning of the OmpF-like porin from Yersinia pseudotuberculosis (YOmpF), we compared the effect of pH variation on the ion channel activity of the protein in planar lipid bilayers and its binding to lipid membranes. The behavior of YOmpF channels upon acidification was similar to that previously described for Escherichia coli OmpF. In particular, a decrease in pH of the bathing solution resulted in a substantial reduction of YOmpF single channel conductance, accompanied by the emergence of subconductance states. Similar subconductance substates were elicited by the addition of lysophosphatidylcholine. This observation, made with porin channels for the first time, pointed to the relevance of lipid-protein interactions, in particular, the lipid curvature stress, to the appearance of subconductance states at acidic pH. Binding of YOmpF to membranes displayed rather modest dependence on pH, whereas the channel-forming potency of the protein tremendously decreased upon acidification.

Exchange of Gramicidin between Lipid Bilayers: Implications for the Mechanism of Channel Formation

“…Mean 5 SD (n ¼ 3). (22), and Rokitskaya et al (23) concluded that gA most likely is able to exchange between lipid bilayers, although definitive proof was lacking.…”

“…An alternative interpretation of the results of Jones et al (12) is that the sustained channel activity was caused by direct transfer of gA from the source LUVs to the interrogated planar bilayer without vesicle fusion. Transfer of gA between lipid vesicles has been proposed previously based on comparisons of the ion release from lipid vesicles and the amount of gA/vesicle (21,22), or the reduction in gA activity after the incubation of gA-containing LUVs with an excess of gA-free vesicles (23), but see (24) for an alternative view. We therefore explored further the possibility that gA is able to undergo facile transfer from one lipid bilayer to another (whether in planar bilayers or lipid vesicles).…”

In Silico Structure and Sequence Analysis of Bacterial Porins and Specific Diffusion Channels for Hydrophilic Molecules: Conservation, Multimericity and Multifunctionality

“…Pore size may vary with environmental factors, e.g., pH-sensitivity of OmpF and OmpG channels [ 44 , 45 ]. Some of the structures analyzed have been proven to be in a closed state (e.g., OmpA, OccD1 and D2).…”

Biogenesis, transport and remodeling of lysophospholipids in Gram-negative bacteria

“…In the presence of LPC, the OmpF-like porin of Y. pseudotubeduclosis alters its ion channel activity and the large-conductance mechanosensitive channel MscL of E. coli is trapped in the fully open state (62,63). In both cases, the mechanisms are proposed to involve intrinsic membrane curvature stress and the resulting physical distortion of the lipid bilayer induced by incorporation of the LPL.…”