Document Detail

Volume enlargement and recovery of Na+-dependent amino acid transport in proteoliposomes derived from Ehrlich ascites cell membranes.
MedLine Citation:
PMID:  3372516     Owner:  NLM     Status:  MEDLINE    
Na+-dependent amino acid transport can be reconstituted from solubilized Ehrlich cell plasma membranes by addition of asolectin vesicles, gel filtration, and a freeze-thaw cycle. Removal of phosphatidic acid (approximately 10% of the total lipid) by Ba2+ precipitation reduces the efficiency of reconstitution of Na+-dependent amino acid transport by approximately 73% and decreases intravesicular volume of the proteoliposomes by approximately 43%. The loss of transport activity is not due to exclusion of specific proteins during reconstitution. The phosphatidic acid-free liposomes are less permeable and require more time to attain an equilibrium distribution of solute. Transport activity and intravesicular volume can be restored to Ba2+-precipitated asolectin proteoliposomes by addition of egg-phosphatidic acid during reconstitution. The extent of recovery of transport activity is proportional to the change in intravesicular volume and depends on the amount of phosphatidic acid present. Replacement of phosphatidic acid with 20% phosphatidylserine or phosphatidylglycerol leads to increases in intravesicular volume with little or no increase in amino acid transport. Generation of phosphatidic acid in situ by treatment of Ba2+-precipitated proteoliposomes with phospholipase D also restored transport. The observed increase in transport activity (9-fold) is accompanied by a 46% increase in intravesicular volume, presumably caused by vesicle fusion. Phosphatidic acid is also required for successful reconstitution of Na+-dependent amino acid transport from pure phosphatidylcholine:phosphatidylethanolamine (1:1) mixtures with only a small change (approximately 16%) in intravesicular volume. The results provide evidence for both indirect and direct effects of phosphatidic acid on reconstitution of Na+-dependent amino acid transport. The indirect effects occur through enlargement of intravesicular volume, large vesicles showing higher rates of transport. However, there is also evidence to indicate a specific effect of phosphatidic acid on the Na+-dependent amino acid transporter, since other acidic lipids may change intravesicular volume without a commensurate change in transport activity.
J I McCormick; R M Johnstone
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  263     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1988 Jun 
Date Detail:
Created Date:  1988-07-13     Completed Date:  1988-07-13     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  8111-9     Citation Subset:  IM    
McGill University, Department of Biochemistry, Montreal, Quebec, Canada.
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MeSH Terms
Amino Acids / metabolism*
Aminoisobutyric Acids / metabolism
Biological Transport, Active
Carcinoma, Ehrlich Tumor / metabolism*
Cell Membrane / metabolism
Phospholipids / analysis
Proteolipids / metabolism*
Sodium / metabolism*
Reg. No./Substance:
0/Amino Acids; 0/Aminoisobutyric Acids; 0/Phosphatidylcholines; 0/Phospholipids; 0/Proteolipids; 0/proteoliposomes; 62-57-7/2-aminoisobutyric acid; 69279-91-0/asolectin; 7440-23-5/Sodium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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