{"doi":"10.1073/pnas.69.5.1100","title":"Detection and Isolation of the Repressor Protein for the Tryptophan Operon of\n            <i>Escherichia coli</i>","abstract":"<jats:p>\n            DNA from a transducing bacteriophage carrying a fusion of the tryptophan and lactose operons of\n            <jats:italic>E. coli</jats:italic>\n            (λd\n            <jats:italic>trp-lac</jats:italic>\n            ) has been used to direct cell-free synthesis of β-galactosidase (EC 3.2.1.23). Whereas normal\n            <jats:italic>lac</jats:italic>\n            operon (λd\n            <jats:italic>lac</jats:italic>\n            ) DNA requires adenosine-3′:5′-cyclic monophosphate (cAMP) for β-galactosidase synthesis,\n            <jats:italic>trp-lac</jats:italic>\n            DNA is unaffected by cAMP. This difference in cAMP dependence verifies the presence of a cAMP-requiring promoter in the\n            <jats:italic>lac</jats:italic>\n            operon that has been removed from the\n            <jats:italic>trp-lac</jats:italic>\n            DNA. Synthesis with\n            <jats:italic>trp-lac</jats:italic>\n            DNA is controlled by the protein product of the tryptophan repressor gene (\n            <jats:italic>trpR</jats:italic>\n            ). Synthesis in extracts of\n            <jats:italic>trpR</jats:italic>\n            <jats:sup>-</jats:sup>\n            (repressor-negative) cells is progressively reduced by increased additions of extract from\n            <jats:italic>trpR</jats:italic>\n            <jats:sup>+</jats:sup>\n            cells. No\n            <jats:italic>trpR</jats:italic>\n            <jats:sup>-</jats:sup>\n            product repression is seen when β-galactosidase synthesis is programmed by normal\n            <jats:italic>lac</jats:italic>\n            DNA. This highly sensitive and specific assay has facilitated quantitation and partial purification of the\n            <jats:italic>trp</jats:italic>\n            repressor.\n          </jats:p>","journal":"Proceedings of the National Academy of Sciences","year":1972,"id":14879,"datarank":7.659365821258547,"base_score":4.820281565605037,"endowment":4.820281565605037,"self_citation_contribution":0.7230422348407557,"citation_network_contribution":6.936323586417791,"self_endowment_contribution":0.7230422348407557,"citer_contribution":6.936323586417791,"corpus_percentile":null,"corpus_rank":null,"citation_count":123,"citer_count":115,"citers_with_citation_signal":107,"citers_with_endowment":107,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":115607,"name":"Daniel E. Morse","orcid":null,"position":1,"is_corresponding":false},{"id":115608,"name":"W. Jurgen Schrenk","orcid":null,"position":2,"is_corresponding":false},{"id":115609,"name":"J. H. M. Miller","orcid":null,"position":3,"is_corresponding":false},{"id":115529,"name":"G. Zubay","orcid":null,"position":0,"is_corresponding":false}],"reference_count":0,"raw_metadata":{"has_enrichment":true,"base_score":4.820281565605037,"endowment":4.820281565605037,"datacite_reuse_total":0,"file_count":0,"downloads":0,"views":0,"has_version_chain":false,"is_dataset":false,"is_oa":false,"pmid":"4338582","pmcid":"PMC426639","openalex_id":"https://openalex.org/W2029129282","authors":[],"funders":[],"total_grants":0,"fwci":7.6787,"citation_percentile":0.98129185,"influential_citations":2,"citation_trend":[{"year":2012,"count":2},{"year":2013,"count":3},{"year":2014,"count":3},{"year":2016,"count":7},{"year":2017,"count":1},{"year":2018,"count":2},{"year":2019,"count":3},{"year":2020,"count":6},{"year":2021,"count":4},{"year":2022,"count":1},{"year":2023,"count":1},{"year":2024,"count":2},{"year":2025,"count":2}],"oa_status":"bronze","license":null,"oa_locations":[{"url":"https://www.pnas.org/content/pnas/69/5/1100.full.pdf","host_type":"journal"},{"url":"https://www.pnas.org/content/pnas/69/5/1100.full.pdf","host_type":"BRONZE"},{"url":"https://www.pnas.org/content/pnas/69/5/1100.full.pdf","host_type":"publisher"},{"url":"https://pnas.org/doi/pdf/10.1073/pnas.69.5.1100","host_type":"publisher"},{"url":"https://doi.org/10.1073/pnas.69.5.1100","host_type":"journal"},{"url":"https://pubmed.ncbi.nlm.nih.gov/4338582","host_type":"repository"},{"url":"https://www.ncbi.nlm.nih.gov/pmc/articles/426639","host_type":"repository"}],"fields_of_study":["Biochemical and Molecular Research","Amino Acid Enzymes and Metabolism","Carbohydrate Chemistry and Synthesis","Medicine","Biology","Bacterial Proteins","Cell-Free System","Coliphages","Cyclic AMP","DNA, Bacterial","DNA, Viral","Escherichia coli","Galactosidases","Genes, Regulator","Genetic Code","Genotype","Lactose","Operon","Transduction, Genetic","Tryptophan"],"mesh_terms":["Cyclic AMP","Bacterial Proteins","Cell-Free System","Coliphages","DNA, Bacterial","DNA, Viral","Escherichia coli","Galactosidases","Genes, Regulator","Genetic Code","Genotype","Lactose","Operon","Transduction, Genetic","Tryptophan"],"keywords":["trp operon","Lac repressor","lac operon","Operon","Repressor","gal operon","Escherichia coli","DNA","Biochemistry","Tryptophan","Beta-galactosidase","L-arabinose operon","Molecular biology","Derepression","Biology","Chemistry","Gene","Psychological repression","Gene expression","Amino acid"],"sdg_mappings":[],"linked_datasets":[],"clinical_trials":[],"software_tools":[],"database_accessions":[],"source":"live","citation_network_status":"fetched"},"created_at":"2026-06-01T15:18:35.540509Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}