Oligomeric structure of a renal cystine transporter: implications in cystinuria.
Homologous proteins (NBAT) which mediate sodium-independent transport of neutral as well as basic amino acids and cystine when expressed in Xenopus oocytes were recently cloned from mammalian kidneys. Mutations in human NBAT have been implicated in cystinuria. Here, we show that rat kidney and jejunal brush border membrane NBAT (85 kDa) is found in association with a 50 kDa protein. The association involves one or more interprotein disulfide bonds. Rabbit kidney brush border membranes and membranes of NBAT cRNA-injected Xenopus oocytes also contain such heterodimers. Our data suggest that the heterodimer is the minimal functional unit of NBAT-mediated amino acid transport and that the NBAT-associated 50 kDa protein could play a role in cystinuria.
Wang
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Department of Biochemistry, Cornell University Medical College, New York, NY 10021, USA.
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D026923:Amino Acid Transport Systems, Basic; D026921:Amino Acid Transport Systems, Neutral; D000818:Animals; D001693:Biological Transport, Active; D015153:Blotting, Western; D002352:Carrier Proteins / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D003432:Cross-Linking Reagents; D003553:Cystine / Q000378:metabolism*; D003555:Cystinuria / Q000378:metabolism*; D004120:Dimethyl Suberimidate; D006801:Humans; D007583:Jejunum / Q000737:chemistry; D007668:Kidney / Q000737:chemistry / Q000378:metabolism*; D008871:Microvilli / Q000737:chemistry; D008970:Molecular Weight; D009865:Oocytes; D011487:Protein Conformation; D018075:RNA, Complementary; D011817:Rabbits; D051381:Rats; D014982:Xenopus laevis
D026923:Amino Acid Transport Systems, Basic; D026921:Amino Acid Transport Systems, Neutral; D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D018075:RNA, Complementary; C489857:SLC3A1 protein, human; C081009:Slc3a1 protein, rat; D004120:Dimethyl Suberimidate; D003553:Cystine