Two novel oligopeptide transporter cDNA clones, CPTA and CPTB, were identified by screening a Caenorhabditis elegans cDNA library using homology hybridization. The transporter proteins deduced from the cDNAs possess multiple transmembrane domains and reveal a moderate similarity to their mammalian counterparts in amino acid sequences. CPTA and CPTB, when expressed in Xenopus laevis oocytes and studied by both radiotracer flux and microelectrode voltage-clamp protocol, displayed a saturable electrogenic transport activity driven by a proton gradient with an overlapping broad spectrum of substrate specificity. Both transporters recognize di-, tri- and tetra-peptides including phenylalanylmethionylarginylphenylalaninamide (FMRFamide) and N-acetylaspartylglutamate, members of a large neuropeptide family commonly found throughout the animal kingdom. Kinetic analysis, however, revealed that CPTA and CPTB differed in their affinity for the peptide substrates, the former being a high-affinity type and the latter a low-affinity type. CPTA and CPTB are encoded by two distinct genes localized on separate chromosomes and are expressed during the whole life span of the organism.
Two oligopeptide transporters from Caenorhabditis elegans:molecular cloning and functional expression
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You-Jun FEI, Takuya FUJITA, David F. LAPP, Vadivel GANAPATHY, Frederick H. LEIBACH; Two oligopeptide transporters from Caenorhabditis elegans:molecular cloning and functional expression. Biochem J 1 June 1998; 332 (2): 565–572. doi: https://doi.org/10.1042/bj3320565
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