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  • Articles: DFG German National Licenses  (2)
  • 1995-1999  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Attenuation of channel kinetics and conductance by cholesterol: An interpretation using structural stress as a unifying concept (1995)
    Springer
    The journal of membrane biology 143 (1995), S. 51-63 
    Details
    ISSN: 1432-1424
    Keywords: Calcium-activated potassium channel ; Cholesterol ; Conductance ; Lateral elastic stress ; Lipid bilayers ; Lipid-channel interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The ubiquity of cholesterol in cell membranes and changes in its concentration during development, aging and in various diseases suggest that it plays an important role in modulating cell function. We examined this possibility by monitoring the effects of cholesterol on the activity of the calcium-activated potassium (BK) channel reconstituted into lipid bilayers from rat brain homogenates. Increasing the cholesterol concentration to 11% of total lipid weight resulted in a 70% reduction in channel mean open time and a reduction of the open probability of the channel by 80%. Channel conductance was reduced by 7%. Cholesterol is known to change the order state and the modulus of compressibility of bilayers. These physico-chemical changes may be translated into an overall increase in the structural stress in the bilayer, and this force may be transmitted to proteins residing therein. By examining the characteristics of the BK channel as a function of temperature, in the presence and absence of cholesterol, we were able to estimate the activation energy based on Arrhenius plots of channel kinetics. Cholesterol reduced the activation energy of the BK channel by 50% for the open to closed transition. This result is consistent with an increased stress energy in the bilayer and favors the channel moving into the closed state. Taken together, these data are consistent with a model in which cholesterol induces structural stress which enhances the transition from the open to the closed state of the channel. We suggest that this is an important mechanism for regulating the activity of membrane-integral proteins and therefore membrane function, and that the concept of structural stress may be relevant to understanding the modulation of ion channel activity in cell membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232523
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Lipid-ion channel interactions: Increasing phospholipid headgroup size but not ordering acyl chains alters reconstituted channel behavior (1995)
    Springer
    The journal of membrane biology 145 (1995), S. 13-19 
    Details
    ISSN: 1432-1424
    Keywords: Lipid-protein interactions ; Elastic stress ; Curvature stress ; Reconstituted potassium channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We have recently shown (Chang et al., 1995) that lipid-channel interactions, exemplified by the effects of cholesterol on the calcium-activated potassium (BK) channel, profoundly affect channel properties. The present study further explores such interactions by monitoring changes in BK channel behavior after reconstitution into bilayers where the size of phospholipid (PL) headgroups is increased and where the freedom of motion (inverse order) of fatty acid chains is incremented. Increasing the PL headgroup cross-sectional area, from that of N-meth-DOPE to that of DOPC (an increase from ca. 60 to 70 Å2), is associated with a doubling of the channel mean opentime. Channel conductance, however, was unaffected. Increasing the order of the fatty acid chains, from that of DOPE to POPE and to that of DEPE, had no significant effect on channel properties (at 22°C). We interpret the changes reported here to reflect lipid-protein interactions through the induction of structural stress related to the headgroup structures of phospholipids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233303
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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