{"doi":"10.1021/acs.biochem.4c00046","title":"NMR Structure of Retinal Guanylate Cyclase Activating Protein 5 (GCAP5) with R22A Mutation That Abolishes Dimerization and Enhances Cyclase Activation","abstract":"Guanylate cyclase activating protein-5 (GCAP5) in zebrafish photoreceptors promotes the activation of membrane receptor retinal guanylate cyclase (GC-E). Previously, we showed the R22A mutation in GCAP5 (GCAP5 R22A ) abolishes dimerization of GCAP5 and activates GC-E by more than 3-fold compared to that of wild-type GCAP5 (GCAP5 WT ). Here, we present ITC, NMR, and functional analysis of GCAP5 R22A to understand how R22A causes a decreased dimerization affinity and increased cyclase activation. ITC experiments reveal GCAP5 R22A binds a total of 3 Ca 2+, including two sites in the nanomolar range followed by a single micromolar site. The two nanomolar sites in GCAP5 WT were not detected by ITC, suggesting that R22A may affect the binding of Ca 2+ to these sites. The NMR-derived structure of GCAP5 R22A is overall similar to that of GCAP5 WT (RMSD = 2.3 Å), except for local differences near R22A (Q19, W20, Y21, and K23) and an altered orientation of the C-terminal helix near the N-terminal myristate. GCAP5 R22A lacks an intermolecular salt bridge between R22 and D71 that may explain the weakened dimerization. We present a structural model of GCAP5 bound to GC-E in which the R22 side-chain contacts exposed hydrophobic residues in GC-E. Cyclase assays suggest that GC-E binds to GCAP5 R22A with ∼25% higher affinity compared to GCAP5 WT, consistent with more favorable hydrophobic contact by R22A that may help explain the increased cyclase activation.","journal":"Biochemistry","year":2024,"id":497030,"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":0.9466,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2024-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":444347,"name":"Effibe O. Ahoulou","orcid":null,"position":1,"is_corresponding":false},{"id":928599,"name":"Aritra Bej","orcid":"0000-0002-5561-1891","position":2,"is_corresponding":false},{"id":1343947,"name":"Annika N. Janssen","orcid":null,"position":3,"is_corresponding":false},{"id":794429,"name":"Alexander Scholten","orcid":null,"position":4,"is_corresponding":false},{"id":793849,"name":"Karl‐Wilhelm Koch","orcid":"0000-0003-1501-0044","position":5,"is_corresponding":false},{"id":482649,"name":"James B. Ames","orcid":"0000-0003-0934-2595","position":6,"is_corresponding":false},{"id":794428,"name":"Diana Cudia","orcid":null,"position":0,"is_corresponding":true}],"reference_count":58,"raw_metadata":null,"created_at":"2026-07-19T02:09:30.779495Z","pmid":"38662574","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":[]}