Abstract:
:The functional role of distinct phospholipid subclasses and molecular species in modulating gramicidin-mediated K+ flux was characterized through quantification of changes in the fluorescence intensity of ion specific fluorescent probes encapsulated inside vesicles comprised of individual molecular species of plasmenylcholine and phosphatidylcholine. The rate constant of gramicidin-mediated K+ ion flux across bilayers comprised of 1-O-(Z)-hexadec-1'-enyl-2-octadec-9'-enoyl-sn-glycero-3-p hos phocholine (plasmenylcholine) was 18.9 +/- 1.7 s-1, while that present across bilayers comprised of 1-hexadecanoyl-2-octadec-9'-enoyl-sn-glycero-3-phosphocholine (phosphatidylcholine) was 12.3 +/- 1.5 s-1. The observed changes were not due to alterations in the nature of the sn-2 aliphatic chain or the net surface charge present at the membrane interface and were unaltered by the addition of several amphiphilic agents (including charged amphiphiles), suggesting that the observed alterations specifically reflect changes in channel function which result from the covalent alteration of host phospholipid in the proximal portion of the sn-1 aliphatic chain (i.e., phospholipid subclass-specific alterations). Addition of cholesterol to bilayer matrices comprised of plasmenylcholine resulted in dose-dependent attenuation of the rate of gramicidin-mediated K+ flux, but did not alter the rate of gramicidin-mediated K+ flux in membranes comprised of phosphatidylcholine. Gramicidin ion channels experience distinct environments in membranes comprised of phosphatidylcholine and plasmenylcholine host lipids demonstrated by both the different fluorescence anisotropies of endogenous tryptophan residues and the different C=O stretching frequencies of intramonomer carbonyls in gramicidin incorporated into these two choline glycerophospholipid subclasses.(ABSTRACT TRUNCATED AT 250 WORDS)
journal_name
Biochemistryjournal_title
Biochemistryauthors
Chen X,Gross RWdoi
10.1021/bi00022a008subject
Has Abstractpub_date
1995-06-06 00:00:00pages
7356-64issue
22eissn
0006-2960issn
1520-4995journal_volume
34pub_type
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