Amino AcidsAmino Acid Transport SystemsReceptors, Purinergic P2X1LeucineSubstance PSequence Homology, Amino AcidAmino Acid SequenceAmino Acid SubstitutionCloning, MolecularAmino Acids, EssentialSequence AlignmentBase SequenceSubstance-Related DisordersMutationMolecular Sequence DataEscherichia coliAmino Acid MotifsKineticsBinding SitesMutagenesis, Site-DirectedNeutral RedPeptide FragmentsDNA, ComplementaryProtein ConformationSequence Homology, Nucleic AcidAmino Acids, AromaticRecombinant ProteinsModels, MolecularAmino Acids, Branched-Chain