Bilayer Thickness Modulates the Conductance of the BK Channel in Model Membranes

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DOIResolve DOI: http://doi.org/10.1529/biophysj.103.029678
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TypeArticle
Journal titleBiophys. J.
Volume86
Issue6
Pages36203633; # of pages: 14
AbstractThe conductance of the BK channel was evaluated in reconstituted bilayers made of POPE/POPS (3.3:1), or POPE/POPS with an added 20% of either SPM (3.3:1:1), CER (3.3:1:1), or CHL (3.3:1:1). The presence of SPM, which is known to increase bilayer thickness, significantly reduced the conductance of the BK channel. To directly test the role of membrane thickness, the conductance of the BK channel was measured in bilayers formed from PCs with acyl chains of increasing length (C14:1-C24:1), all in the absence of SPM. Slope conductance was maximal at a chain length of (C18:1) and much reduced for both thinner (C14:1) and thicker (C24:1) bilayers, indicating that membrane thickness alone can modify slope conductance. Further, in a simplified binary mixture of DOPE/SPM that forms a confined, phase-separated bilayer, the measured conductance of BK channels shows a clear bimodal distribution. In contrast, the addition of CER, which has an acyl chain structure similar to SPM but without its bulky polar head group to POPE/POPS, was without effect, as was the addition of CHL. The surface structure of membranes made from these same lipid mixtures was examined with AFM. Incorporation of both SPM and CER resulted in the formation of microdomains in POPE/POPS monolayers, but only SPM promoted a substantial increase in the amount of the high phase observed for the corresponding bilayers. The addition of CHL to POPE/POPS eliminated the phase separation observed in the POPE/POPS bilayer. The decrease in channel conductance observed with the incorporation of SPM into POPE/POPS membranes was, therefore, attributed to larger SPM-rich domains that appear thicker than the neighboring bilayer.
Publication date
AffiliationNational Research Council Canada; NRC Steacie Institute for Molecular Sciences
Peer reviewedNo
NPARC number12330199
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Record identifierb736daf2-4f19-4d51-bc98-bd3fec8b7ffa
Record created2009-09-10
Record modified2016-05-09
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