Document Detail

Nature of the elements transporting long-chain fatty acids through the red cell membrane.
MedLine Citation:
PMID:  9625774     Owner:  NLM     Status:  MEDLINE    
Docosahexaenoic acid is found to be bound to three equivalent sites on albumin with the same affinities as palmitic acid at 0-38 degreesC, which demonstrates that ethene-1,2-diyl- and methylene-groups contribute equally to the affinity. The equilibrium dissociation constants (Kdms) for red cell membrane binding sites of linoleic- and docosahexaenoic acid at pH 7.3 are determined at temperatures between 0 and 37 degrees C. The temperature-independent capacities for binding are 12 +/- 1 and 25.4 +/- 3.0 nmoles g-1 ghosts respectively. Double isotope binding experiments reveal that the unsaturated fatty acids: arachidonic-, linoleic-, docosahexaenoic-, and oleic acid have partially shared capacities in ratios approximately 1:2:4:5, in contrast to the noncompetitive binding of palmitic acid. The observations suggest a two-tier binding limitation. One is the number of protein sites binding fatty acid anions electrostatically and the other is the number of suitable annular lipids adaptively selected among membrane lipids by the hydrocarbon chain. These competition conditions are confirmed by measurements of the tracer exchange efflux at near 0 degrees C from albumin-free and albumin-filled ghosts of linoleic- and docosahexaenoic acid, either alone or in the presence of arachidonic- and palmitic acid. Under equilibrium conditions, the calculated ratios of inside to outside membrane binding is below 0.5 for four unsaturated fatty acids. The unidirectional rate constants of translocation between the inside and the outside correlate with the number of double bonds in these fatty acids, which are also correlated with the dissociation rate constants of the complexes with albumin. The membrane permeation occurs presumably by binding of the anionic unsaturated fatty acids to an integral protein followed by channeling of the neutral form between opposite binding sites of the protein through annular lipids encircling the protein.
I N Bojesen; E Bojesen
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of membrane biology     Volume:  163     ISSN:  0022-2631     ISO Abbreviation:  J. Membr. Biol.     Publication Date:  1998 Jun 
Date Detail:
Created Date:  1998-09-01     Completed Date:  1998-09-01     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0211301     Medline TA:  J Membr Biol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  169-81     Citation Subset:  IM    
Department of Medical Biochemistry and Genetics, Laboratory of Medical Biochemistry B, University of Copenhagen, The Panum Institute, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark.
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MeSH Terms
Binding, Competitive
Biological Transport
Docosahexaenoic Acids / blood
Erythrocyte Membrane / metabolism*
Fatty Acids / blood*
Fatty Acids, Unsaturated / blood
Protein Binding
Serum Albumin, Bovine / metabolism
Reg. No./Substance:
0/Fatty Acids; 0/Fatty Acids, Unsaturated; 0/Serum Albumin, Bovine; 25167-62-8/Docosahexaenoic Acids

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