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  • 1
    ISSN: 1432-1017
    Keywords: K+ channel ; Chromaffn granule ; Membrane reconstitution ; Planar bilayer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract A K+ channel was incorporated into voltage-clamped planar lipid bilayers from bovine chromaffin granules and resealed granule membranes (“ghosts”). It was not incorporated from plasma membrane-rich fractions from the adrenal medulla. The channel had a conductance of ∼ 400 pS in symmetric 450 mM KCI, with the permeability sequence K+ 〉 Rb+ 〉 Cs+ 〉 Na+ 〉 Li+, and was insensitive to both Ca2+ and charybdotoxin. It exhibited complex gating kinetics, consistent with the presence of multiple open and closed states, and its gating was voltage-dependent. The channels appeared to incorporate into bilayers with the same orientation, and were blocked from one side (the side of vesicle addition) by 0.2-1 mM TEA'. The block was slightly voltage-dependent. Acidification of resealed granule membranes in response to external ATP (which activated the vacuolartype ATPase) was significantly reduced in the presence of 1 mM intralumenal TEACI (with 9 mM KCl), and parallel measurements with the potential-sensitive dye Oxonol V showed that such vesicles tended to develop higher internal-positive membrane potentials than control vesicles containing only 10 mM KCI. 1 mM TEA+ had no effect on proton-pumping activity when applied externally, and did not directly affect either the proton-pumping or ATP hydrolytic activity of the partially-purified ATPase. These results suggest that chromaffin granule membranes contain a TEA+-sensitive K+ channel which may have a role in regulating the vesicle membrane potential.
    Type of Medium: Electronic Resource
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