Two oligopeptide transporters from Caenorhabditis elegans: molecular cloning and functional expression.
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.
Fei
Y J
YJ
Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA. yjfei@mail.mcg.edu
Fujita
T
T
Lapp
D F
DF
Ganapathy
V
V
Leibach
F H
FH
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D017173:Caenorhabditis elegans / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins; D003001:Cloning, Molecular; D004594:Electrophysiology; D004789:Enzyme Activation; D015870:Gene Expression / Q000235:genetics; D015801:Helminth Proteins / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014981:Xenopus
D018528:ATP-Binding Cassette Transporters; D029742:Caenorhabditis elegans Proteins; D015801:Helminth Proteins; D026901:Membrane Transport Proteins; D009842:Oligopeptides; D012333:RNA, Messenger; C113070:pept-1 protein, C elegans; C113069:pept-2 protein, C elegans