CYSTINURIA CALLS FOR HETEROMULTIMERIC AMINO-ACID TRANSPORTERS

The proteins rBAT (related to b(o,+) amino acid transporter) and 4F2hc (the heavy chain of the surface antigen 4F2) are homologous proteins that induce amino acid transport in Xenopus oocytes. The role of rBAT in amino acid transport is substantiated by the fact that mutations in the gene encoding it cause cystinuria, a heritable disease characteri sed by high concentrations of cystine in the urine. Structural and fun ctional evidence supports the hypothesis that both rBAT and 4F2hc prot eins farm part of heterodimeric amino acid transporters. There is new evidence that; the functional unit of system y(+)L amino acid transpor ter is a disulfide bridge-dependent complex of 4F2hc with a Xenopus oo cyte plasma membrane protein.