{"doi":"10.1101/2020.05.03.075317","title":"Regulation of an iron-dependent repressor by tryptophan availability attenuates transcription of the tryptophan salvage genes in <i>Chlamydia trachomatis</i>","abstract":"The trp operon of Chlamydia trachomatis has a genetic organization that is distinct from other model bacteria. The operon contains the trpR open-reading frame (ORF), an intergenic region (IGR), and the trpB and trpA ORFs. TrpR mediates tryptophan-dependent regulation of the operon from the major promoter upstream of trpR (P trpR ). We recently reported that trpBA is additionally regulated by the iron-dependent repressor YtgR via an operator sequence within the IGR upstream of an alternative promoter for TrpR-independent trpBA expression (P trpBA ). Here we report that YtgR repression of P trpBA is also dependent on tryptophan levels via a rare triple-tryptophan motif (WWW) in the N-terminal permease domain of the YtgCR precursor. Tryptophan limitation inhibits translation at the WWW motif and subsequently promotes transcription termination of ytgCR in a Rho-independent manner. This regulatory schematic resembles mechanisms of transcriptional attenuation for trp operons described in model bacteria, such as cis -attenuation by TrpL in E. coli or trans -attenuation by TRAP in B. subtilis. YtgR performs an analogous function by sensing both iron and tryptophan levels, with the latter highlighting the unique strategy of Chlamydia to retain a trans -attenuator mechanism for regulating expression of the trpRBA operon.","journal":"bioRxiv (Cold Spring Harbor Laboratory)","year":2020,"id":129574,"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":0,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9547,"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":419239,"name":"Nathan D. Hatch","orcid":null,"position":1,"is_corresponding":false},{"id":326294,"name":"Scot P. Ouellette","orcid":"0000-0002-3721-6839","position":2,"is_corresponding":false},{"id":418390,"name":"Rey A. Carabeo","orcid":"0000-0002-5708-5493","position":3,"is_corresponding":false},{"id":418389,"name":"Nick D. Pokorzynski","orcid":"0000-0003-2438-2368","position":0,"is_corresponding":true}],"reference_count":70,"raw_metadata":null,"created_at":"2026-07-18T23:15:49.682497Z","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":[]}