{"doi":"10.3389/fmolb.2021.728711","title":"Reactivity of Thiol-Rich Zn Sites in Diacylglycerol-Sensing PKC C1 Domain Probed by NMR Spectroscopy","abstract":"Conserved homology 1 (C1) domains are peripheral zinc finger domains that are responsible for recruiting their host signaling proteins, including Protein Kinase C (PKC) isoenzymes, to diacylglycerol-containing lipid membranes. In this work, we investigated the reactivity of the C1 structural zinc sites, using the cysteine-rich C1B regulatory region of the PKCα isoform as a paradigm. The choice of Cd 2+ as a probe was prompted by previous findings that xenobiotic metal ions modulate PKC activity. Using solution NMR and UV-vis spectroscopy, we found that Cd 2+ spontaneously replaced Zn 2+ in both structural sites of the C1B domain, with the formation of all-Cd and mixed Zn/Cd protein species. The Cd 2+ substitution for Zn 2+ preserved the C1B fold and function, as probed by its ability to interact with a potent tumor-promoting agent. Both Cys 3 His metal-ion sites of C1B have higher affinity to Cd 2+ than Zn 2+ , but are thermodynamically and kinetically inequivalent with respect to the metal ion replacement, despite the identical coordination spheres. We find that even in the presence of the oxygen-rich sites presented by the neighboring peripheral membrane-binding C2 domain, the thiol-rich sites can successfully compete for the available Cd 2+ . Our results indicate that Cd 2+ can target the entire membrane-binding regulatory region of PKCs, and that the competition between the thiol- and oxygen-rich sites will likely determine the activation pattern of PKCs.","journal":"Frontiers in Molecular Biosciences","year":2021,"id":207670,"datarank":0.2987842850601337,"base_score":1.791759469228055,"endowment":1.791759469228055,"self_citation_contribution":0.26876392038420827,"citation_network_contribution":0.030020364675925455,"self_endowment_contribution":0.26876392038420827,"citer_contribution":0.030020364675925455,"corpus_percentile":null,"corpus_rank":null,"citation_count":5,"citer_count":4,"citers_with_citation_signal":3,"citers_with_endowment":3,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.959,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":451304,"name":"Tatyana I. Igumenova","orcid":"0000-0003-3772-7484","position":1,"is_corresponding":false},{"id":689967,"name":"Taylor R. Cole","orcid":null,"position":0,"is_corresponding":true}],"reference_count":64,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-18T23:51:49.715594Z","pmid":"34447788","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":[]}