{"doi":"10.7554/elife.92462","title":"Mobile barrier mechanisms for Na+-coupled symport in an MFS sugar transporter","abstract":"While many 3D structures of cation-coupled transporters have been determined, the mechanistic details governing the obligatory coupling and functional regulations still remain elusive. The bacterial melibiose transporter (MelB) is a prototype of major facilitator superfamily transporters. With a conformation-selective nanobody, we determined a low-sugar affinity inward-facing Na + -bound cryoEM structure. The available outward-facing sugar-bound structures showed that the N- and C-terminal residues of the inner barrier contribute to the sugar selectivity. The inward-open conformation shows that the sugar selectivity pocket is also broken when the inner barrier is broken. Isothermal titration calorimetry measurements revealed that this inward-facing conformation trapped by this nanobody exhibited a greatly decreased sugar-binding affinity, suggesting the mechanisms for substrate intracellular release and accumulation. While the inner/outer barrier shift directly regulates the sugar-binding affinity, it has little or no effect on the cation binding, which is supported by molecular dynamics simulations. Furthermore, the hydron/deuterium exchange mass spectrometry analyses allowed us to identify dynamic regions; some regions are involved in the functionally important inner barrier-specific salt-bridge network, which indicates their critical roles in the barrier switching mechanisms for transport. These complementary results provided structural and dynamic insights into the mobile barrier mechanism for cation-coupled symport.","journal":"eLife","year":2023,"id":345289,"datarank":0.42531735461608655,"base_score":2.639057329615259,"endowment":2.639057329615259,"self_citation_contribution":0.3958585994422889,"citation_network_contribution":0.029458755173797674,"self_endowment_contribution":0.3958585994422889,"citer_contribution":0.029458755173797674,"corpus_percentile":null,"corpus_rank":null,"citation_count":13,"citer_count":3,"citers_with_citation_signal":1,"citers_with_endowment":1,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9337,"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":457007,"name":"Yuqi Shi","orcid":"0009-0000-0825-7933","position":1,"is_corresponding":false},{"id":722130,"name":"Satoshi Katsube","orcid":"0000-0002-3312-7476","position":2,"is_corresponding":false},{"id":1085269,"name":"Katleen Willibal","orcid":null,"position":3,"is_corresponding":false},{"id":1084749,"name":"Nathan D. Burrows","orcid":"0000-0002-3973-1017","position":4,"is_corresponding":false},{"id":286104,"name":"Patrick Mitchell","orcid":"0000-0002-3458-6930","position":5,"is_corresponding":false},{"id":1084750,"name":"Amirhossein Bakhtiiari","orcid":"0000-0002-3979-0973","position":6,"is_corresponding":false},{"id":1085270,"name":"Samantha Stanfield","orcid":null,"position":7,"is_corresponding":false},{"id":263120,"name":"Els Pardon","orcid":"0000-0002-2466-0172","position":8,"is_corresponding":false},{"id":519647,"name":"H. Ronald Kaback","orcid":"0000-0003-0683-5810","position":9,"is_corresponding":false},{"id":630200,"name":"Ruibin Liang","orcid":"0000-0001-8741-1520","position":10,"is_corresponding":false},{"id":263123,"name":"Jan Steyaert","orcid":"0000-0002-3825-874X","position":11,"is_corresponding":false},{"id":89978,"name":"Rosa Viner","orcid":"0000-0003-0550-5545","position":12,"is_corresponding":false},{"id":563736,"name":"Lan Guan","orcid":"0000-0002-2274-361X","position":13,"is_corresponding":false},{"id":587009,"name":"Parameswaran Hariharan","orcid":"0000-0002-6020-1547","position":0,"is_corresponding":true}],"reference_count":88,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-19T01:11:39.484741Z","pmid":"38381130","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":[]}