{"doi":"10.1074/jbc.ra120.016278","title":"The flexible N-terminus of BchL autoinhibits activity through interaction with its [4Fe-4S] cluster and released upon ATP binding","abstract":"A key step in bacteriochlorophyll biosynthesis is the reduction of protochlorophyllide to chlorophyllide, catalyzed by dark-operative protochlorophyllide oxidoreductase. Dark-operative protochlorophyllide oxidoreductase contains two [4Fe-4S]-containing component proteins (BchL and BchNB) that assemble upon ATP binding to BchL to coordinate electron transfer and protochlorophyllide reduction. But the precise nature of the ATP-induced conformational changes is poorly understood. We present a crystal structure of BchL in the nucleotide-free form where a conserved, flexible region in the N-terminus masks the [4Fe-4S] cluster at the docking interface between BchL and BchNB. Amino acid substitutions in this region produce a hyperactive enzyme complex, suggesting a role for the N-terminus in autoinhibition. Hydrogen-deuterium exchange mass spectrometry shows that ATP binding to BchL produces specific conformational changes leading to release of the flexible N-terminus from the docking interface. The release also promotes changes within the local environment surrounding the [4Fe-4S] cluster and promotes BchL-complex formation with BchNB. A key patch of amino acids, Asp-Phe-Asp (the 'DFD patch'), situated at the mouth of the BchL ATP-binding pocket promotes intersubunit cross stabilization of the two subunits. A linked BchL dimer with one defective ATP-binding site does not support protochlorophyllide reduction, illustrating nucleotide binding to both subunits as a prerequisite for the intersubunit cross stabilization. The masking of the [4Fe-4S] cluster by the flexible N-terminal region and the associated inhibition of the activity is a novel mechanism of regulation in metalloproteins. Such mechanisms are possibly an adaptation to the anaerobic nature of eubacterial cells with poor tolerance for oxygen.","journal":"Journal of Biological Chemistry","year":2020,"id":89501,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":9,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9488,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2020-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":452627,"name":"Syed Muhammad Saad Imran","orcid":"0000-0002-2416-016X","position":1,"is_corresponding":false},{"id":452628,"name":"Maxwell B. Watkins","orcid":"0000-0003-4559-2049","position":2,"is_corresponding":false},{"id":452629,"name":"J.P. Bacik","orcid":"0000-0001-9315-5332","position":3,"is_corresponding":false},{"id":453767,"name":"Jenna R. Mattice","orcid":null,"position":4,"is_corresponding":false},{"id":453768,"name":"Angela Patterson","orcid":null,"position":5,"is_corresponding":false},{"id":453769,"name":"Karamatullah Danyal","orcid":null,"position":6,"is_corresponding":false},{"id":453770,"name":"Mark Soffe","orcid":null,"position":7,"is_corresponding":false},{"id":452630,"name":"Robert Kitelinger","orcid":"0000-0002-6460-4335","position":8,"is_corresponding":false},{"id":452631,"name":"Lance C. Seefeldt","orcid":"0000-0002-6457-9504","position":9,"is_corresponding":false},{"id":452632,"name":"Sofia Origanti","orcid":"0000-0002-6953-0160","position":10,"is_corresponding":false},{"id":452633,"name":"Brian Bennett","orcid":"0000-0003-2688-1478","position":11,"is_corresponding":false},{"id":316553,"name":"Brian Bothner","orcid":"0000-0003-1295-9609","position":12,"is_corresponding":false},{"id":329706,"name":"Nozomi Ando","orcid":"0000-0001-7062-1644","position":13,"is_corresponding":false},{"id":452634,"name":"Edwin Antony","orcid":"0000-0002-1888-054X","position":14,"is_corresponding":false},{"id":452626,"name":"Elliot I. Corless","orcid":"0000-0002-5033-0601","position":0,"is_corresponding":true}],"reference_count":47,"raw_metadata":null,"created_at":"2026-07-18T22:02:27.195966Z","pmid":"33219127","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":[]}