Amino Acids, CyclicAmino AcidsSequence Homology, Amino AcidAmino Acid SequenceAmino Acid SubstitutionCloning, MolecularEscherichia coliBase SequenceAmino Acids, EssentialKineticsMutationMolecular Sequence DataProtein BiosynthesisAmino Acid Transport SystemsSequence AlignmentLeucineDNARNA, MessengerBinding SitesAmino Acid MotifsCell LineBacterial ProteinsStructure-Activity RelationshipRecombinant ProteinsMutagenesis, Site-DirectedDNA, ComplementaryModels, MolecularMolecular WeightSequence Homology, Nucleic AcidPeptide FragmentsAmino Acids, Branched-ChainStereoisomerismAmino Acids, AromaticSubstrate SpecificityProtein ConformationPeptidesProtein BindingElectrophoresis, Polyacrylamide GelAmino Acids, SulfurMolecular StructureProtein Structure, TertiaryTranscription, GeneticProteinsCells, Cultured