Bilayer thickness modulates the conductance of the BK channel in model membranes
O'Connell, Robert J.
Feinberg-Zadek, Paula Leslie
Johnston, Linda J.
Treistman, Steven N.
Student AuthorsPaula L. Feinberg-Zadek
UMass Chan AffiliationsGraduate School of Biomedical Sciences, Neuroscience Program
Document TypeJournal Article
*Image Processing, Computer-Assisted
Ion Channel Gating
Large-Conductance Calcium-Activated Potassium Channels
Microscopy, Atomic Force
Potassium Channels, Calcium-Activated
Neuroscience and Neurobiology
MetadataShow full item record
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.
Biophys J. 2004 Jun;86(6):3620-33. Link to article on publisher's site
Permanent Link to this Itemhttp://hdl.handle.net/20.500.14038/39851
Co-author Paula L. Feinberg-Zadek is a student in the Neuroscience program in the Graduate School of Biomedical Sciences (GSBS) at UMass Medical School.