{"doi":"10.1002/pro.4606","title":"Binding by calmodulin is coupled to transient unfolding of the third <scp>FF</scp> domain of <scp>Prp40A</scp>","abstract":"Abstract Human pre‐mRNA processing protein 40 homolog A (hPrp40A) is a splicing factor that interacts with the Huntington's disease protein huntingtin (Htt). Evidence has accumulated that both Htt and hPrp40A are modulated by the intracellular Ca 2+ sensor calmodulin (CaM). Here we report characterization of the interaction of human CM with the third FF domain (FF 3 ) of hPrp40A using calorimetric, fluorescence and structural approaches. Homology modeling, differential scanning calorimetry and small angle X‐ray scattering (SAXS) data show FF 3 forms a folded globular domain. CaM was found to bind FF 3 in a Ca 2+ ‐dependent manner with a 1:1 stoichiometry and a dissociation constant ( K d ) of 25 ± 3 μM at 25°C. NMR studies showed that both domains of CaM are engaged in binding and SAXS analysis of the FF 3 ‐CaM complex revealed CaM occupies an extended configuration. Analysis of the FF 3 sequence showed that the anchors for CaM binding must be buried in its hydrophobic core, suggesting that binding to CaM requires unfolding of FF 3 . Trp anchors were proposed based on sequence analysis and confirmed by intrinsic Trp fluorescence of FF 3 upon binding of CaM and substantial reductions in affinity for Trp‐Ala FF 3 mutants. The consensus model of the complex showed that binding to CaM binding occurs to an extended, non‐globular state of the FF 3 , consistent with coupling to transient unfolding of the domain. The implications of these results are discussed in the context of the complex interplay of Ca 2+ signaling and Ca 2+ sensor proteins in modulating Prp40A‐Htt function.","journal":"Protein Science","year":2023,"id":381566,"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":3,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9698,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2023-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":573369,"name":"John J. Cordoba","orcid":null,"position":1,"is_corresponding":false},{"id":1147562,"name":"Brian Ferrer","orcid":"0000-0003-0500-146X","position":2,"is_corresponding":false},{"id":1134811,"name":"Swati Balakrishnan","orcid":"0000-0002-2903-0604","position":3,"is_corresponding":false},{"id":1147563,"name":"Jennifer E. Wurm","orcid":"0000-0002-0566-3845","position":4,"is_corresponding":false},{"id":1147564,"name":"Belinda Pastrana‐Ríos","orcid":"0000-0002-2114-1182","position":5,"is_corresponding":false},{"id":410984,"name":"Walter Chazin","orcid":"0000-0002-2180-0790","position":6,"is_corresponding":false},{"id":1147561,"name":"Adalberto Díaz Casas","orcid":"0000-0002-9470-6666","position":0,"is_corresponding":true}],"reference_count":45,"raw_metadata":null,"created_at":"2026-07-19T01:17:12.933204Z","pmid":"36810829","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":[]}