{"doi":"10.7554/elife.108335","title":"Allosteric effects of the coupling cation in melibiose transporter MelB","abstract":"The major facilitator superfamily (MFS) transporters play significant roles in human health and disease. Salmonella enterica serovar Typhimurium melibiose permease (MelB St ) catalyzes the symport of galactosides with Na + , H + , or Li + and is a prototype of MFS transporters. We published the structures of MelB St in both inward- and outward-facing conformations, bound to galactoside or Na + , and proposed that positive cooperativity of the co-transported solutes is crucial for the symport mechanism. Here, we elucidated the underlying mechanisms by analyzing MelB St dynamics and the effects of melibiose, Na + , or both using hydrogen-deuterium exchange mass spectrometry (HDX-MS). We also refined the determinants of sugar recognition by solving the crystal structures of a uniporter D59C MelB St complexed with melibiose and other sugars, and by identifying a critical water molecule involved in sugar recognition. Our integrated studies, combining structures, HDX-MS, and molecular dynamics simulations, support the conclusion that sugar-binding affinity is directly correlated with protein dynamics. Na + acts as an allosteric activator, reducing the flexibility of dynamic residues in the sugar-binding site and in the cytoplasmic gating salt-bridge network, thereby increasing sugar-binding affinity. This study provides a molecular-level framework of the symport mechanism that could serve as a general model for cation-coupled symporters.","journal":"eLife","year":2025,"id":575037,"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":0.9615,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2025-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":457007,"name":"Yuqi Shi","orcid":"0009-0000-0825-7933","position":1,"is_corresponding":false},{"id":1084750,"name":"Amirhossein Bakhtiiari","orcid":"0000-0002-3979-0973","position":2,"is_corresponding":false},{"id":630200,"name":"Ruibin Liang","orcid":"0000-0001-8741-1520","position":3,"is_corresponding":false},{"id":89978,"name":"Rosa Viner","orcid":"0000-0003-0550-5545","position":4,"is_corresponding":false},{"id":563736,"name":"Lan Guan","orcid":"0000-0002-2274-361X","position":5,"is_corresponding":false},{"id":587009,"name":"Parameswaran Hariharan","orcid":"0000-0002-6020-1547","position":0,"is_corresponding":true}],"reference_count":42,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-19T02:57:44.572630Z","pmid":"41604452","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":[]}