Association of hepatic system A amino acid transporter with the membrane-cytoskeletal proteins ankyrin and fodrin.
System A activity is a highly regulated mechanism for the active transport of zwitterionic amino acids into mammalian cells. Monoclonal antibodies generated against a previously unidentified rat liver plasma membrane-associated protein were shown to immunoprecipitate solubilized System A transport activity. The immunoreactive protein was later determined by immunoblotting and peptide microsequencing to be rat liver alpha-fodrin (non-erythroid spectrin). Antibody against ankyrin, a protein that often serves as a bridge between integral membrane proteins and fodrin, also immunoprecipitated System A transport activity. Fractionation of solubilized plasma membrane proteins on sucrose gradients revealed that the System A transporter co-migrated as a complex with fodrin and ankyrin, even in the presence of detergent and urea. In contrast, the System N amino acid transporter does not co-migrate with ankyrin and fodrin, nor does the anti-fodrin antibody immunoprecipitate System N activity. The present data are the first to demonstrate an association between an organic solute transporter and the membranocytoskeletal proteins ankyrin and fodrin.
Handlogten
M E
ME
Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, JHMHC, Gainesville 32610, USA.
Dudenhausen
E E
EE
Yang
W
W
Kilberg
M S
MS
D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems; D000818:Animals; D017487:Ankyrins / Q000276:immunology / Q000378:metabolism*; D000911:Antibodies, Monoclonal; D002352:Carrier Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D006801:Humans; D007163:Immunosorbent Techniques; D008099:Liver / Q000378:metabolism* / Q000648:ultrastructure; D008840:Microfilament Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D051381:Rats; D017385:Sequence Homology; D013049:Spectrin
D026905:Amino Acid Transport Systems; D017487:Ankyrins; D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D008840:Microfilament Proteins; D013049:Spectrin