{"doi":"10.1073/pnas.73.10.3529","title":"The functional repressor parts of a tetrameric lac repressor-beta-galactosidase chimaera are organized as dimers.","abstract":"<jats:p>The chimaeric protein repressor-galactosidase, in which fully active lac repressor is covalently linked to the active enzyme beta-galactosidase, was used as a system for probing the quaternary structure of lac repressor. Electron micrographs revealed repressor-galactosidase to be a tetrameric aggregate. When lac repressor, alone, was crosslinked with dimethyl suberimidate, dimers, trimers, tetramers, and oligomers of the protein subunit were produced, whereas crosslinking of the tetrameric repressor-galactosidase resulted in the production of only dimers of the chimaera. Treatment of lac repressor with iodine resulted in the formation of protein dimers; the same result was obtained with repressor-galactosidase. After limited proteolysis of lac repressor, no crosslinking was obtained after treatment with dimethyl suberimidate, whereas iodine still produced a covalent linkage. These results are interpreted as evidence that the lac repressor parts of the tetrameric repressor-galactosidase-chimaera are organized as dimers on the tetrameric-beta-galactosidase core. Because this chimaera has been previously shown to have normal repressor activity [B. Müller-Hill and J. Kania (1974) Nature, 249,561-563], we conclude that lac repressor still is biologically active as a dimeric aggregate.</jats:p>","journal":"Proceedings of the National Academy of Sciences","year":1976,"id":18178,"datarank":5.270938473769771,"base_score":4.219507705176107,"endowment":4.219507705176107,"self_citation_contribution":0.6329261557764161,"citation_network_contribution":4.638012317993355,"self_endowment_contribution":0.6329261557764161,"citer_contribution":4.638012317993355,"corpus_percentile":null,"corpus_rank":null,"citation_count":67,"citer_count":64,"citers_with_citation_signal":58,"citers_with_endowment":58,"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,"fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":127338,"name":"D T Brown","orcid":null,"position":1,"is_corresponding":false},{"id":127295,"name":"J Kania","orcid":null,"position":0,"is_corresponding":false}],"reference_count":0,"raw_metadata":{"has_enrichment":true,"base_score":4.219507705176107,"endowment":4.219507705176107,"datacite_reuse_total":0,"file_count":0,"downloads":0,"views":0,"has_version_chain":false,"is_dataset":false,"is_oa":false,"pmid":"790390","pmcid":"PMC431150","openalex_id":"https://openalex.org/W2071142615","authors":[],"funders":[],"total_grants":0,"fwci":1.6198,"citation_percentile":0.82465031,"influential_citations":0,"citation_trend":[{"year":2016,"count":1}],"oa_status":"green","license":null,"oa_locations":[{"url":"https://www.ncbi.nlm.nih.gov/pmc/articles/431150","host_type":"repository"},{"url":"https://europepmc.org/articles/pmc431150?pdf=render","host_type":"GREEN"},{"url":"https://www.ncbi.nlm.nih.gov/pmc/articles/431150","host_type":"repository"},{"url":"https://pnas.org/doi/pdf/10.1073/pnas.73.10.3529","host_type":"publisher"},{"url":"https://doi.org/10.1073/pnas.73.10.3529","host_type":"journal"},{"url":"https://pubmed.ncbi.nlm.nih.gov/790390","host_type":"repository"},{"url":"http://europepmc.org/pmc/articles/PMC431150","host_type":"repository"}],"fields_of_study":["Enzyme Catalysis and Immobilization","Enzyme Structure and Function","Amino Acid Enzymes and Metabolism","Medicine","Biology","Chemistry","Bacterial Proteins","Chemical Phenomena","Chymotrypsin","DNA, Bacterial","Escherichia coli","Galactosidases","Genes, Regulator","Imides","Iodine","Lactose","Microscopy, Electron","Operon","Protein Conformation","Structure-Activity Relationship","Trypsin"],"mesh_terms":["Bacterial Proteins","Chemistry","Chymotrypsin","DNA, Bacterial","Escherichia coli","Galactosidases","Genes, Regulator","Imides","Iodine","Lactose","Microscopy, Electron","Operon","Protein Conformation","Structure-Activity Relationship","Trypsin","Chemical Phenomena"],"keywords":["Repressor","Lac repressor","Beta-galactosidase","lac operon","Protein quaternary structure","Protein subunit","Chemistry","Biochemistry","Biology","Molecular biology","Stereochemistry","Gene","Escherichia coli","Gene expression"],"sdg_mappings":[{"sdg_number":0,"sdg_label":"Clean water and sanitation"}],"linked_datasets":[],"clinical_trials":[],"software_tools":[],"database_accessions":[],"source":"live","citation_network_status":"fetched"},"created_at":"2026-06-03T19:04:44.680277Z","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,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}