Comparison of the effects of certain thiol reagents on alanine transport in plasma membrane vesicles from rat liver and their use in identifying the alanine carrier.
The Na+-dependent uptake of alanine into plasma membrane vesicles from rat liver was inhibited by N-ethylmaleimide (NEM) and by mersalyl. NEM did not inhibit alanine-independent Na+ uptake and the inhibition of alanine transport by NEM was protected by pre-incubation with an excess of substrate. It was therefore concluded that NEM acted by binding to the alanine carrier. A protein of Mr 20 000 was found to bind NEM with a concentration dependence parallel to the NEM inhibition of alanine transport. The inhibition of binding of [3H]NEM to this protein by mersalyl had a concentration dependence similar to that of the inhibition of transport by mersalyl. Preincubation with L-alanine, but not with D-alanine, led to protection of the Mr 20 000 protein from binding NEM. It is concluded that this protein is an essential component of the alanine transport system.
D000409:Alanine / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005033:Ethylmaleimide / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008634:Mersalyl / Q000494:pharmacology*; D009941:Organomercury Compounds / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D002352:Carrier Proteins; D009941:Organomercury Compounds; D008634:Mersalyl; D005033:Ethylmaleimide; D000409:Alanine