{"doi":"10.7554/elife.109624","title":"Insights into substrate binding and utilization by hyaluronan synthase","abstract":"Hyaluronan (HA), a heteropolysaccharide of alternating N -acetylglucosamine (GlcNAc) and glucuronic acid (GlcA), is an essential component of the vertebrate extracellular matrix. HA biosynthesis proceeds via three evolutionarily convergent reaction mechanisms, catalyzed by the membrane-integrated class 1 enzymes that either elongate the non-reducing (NR) or reducing end of HA, as well as the class 2 hyaluronan synthase (HAS), a soluble non-processive enzyme. Class 1-NR HAS, found in both vertebrates and large double-stranded DNA viruses, is monomeric and couples HA polymerization via coordinated transfer of UDP-GlcNAc and UDP-GlcA substrates with the secretion of the nascent HA chain through its own transmembrane channel. How this HAS discriminates between two UDP-sugars using a single active site is a critical, yet unresolved question. Using single-particle cryo-EM, we reveal a two-step process by which the Chlorella virus HAS (CvHAS) recognizes and positions its substrate, UDP-GlcA, for glycosyl transfer. Further, we report greatly diminished turnover of UDP-GlcA in the absence of a primer, distinguishing acceptor-free activity toward UDP-GlcNAc. Lastly, prompted by observation of a dodecyl maltoside bound HAS, we demonstrate the utility of non-canonical acceptors in priming of a UDP-GlcA transfer reaction. Altogether, this work clarifies the molecular basis for HAS’ dual substrate specificity and the role of UDP-GlcA recognition in integrity of HA synthesis.","journal":"eLife","year":2025,"id":559677,"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":1,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"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":"2025-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":1461783,"name":"Julia Karasinska","orcid":null,"position":1,"is_corresponding":false},{"id":509577,"name":"Jochen Zimmer","orcid":"0000-0002-8423-2882","position":2,"is_corresponding":false},{"id":1169097,"name":"Zachery Stephens","orcid":"0009-0001-0140-5304","position":0,"is_corresponding":true}],"reference_count":25,"raw_metadata":null,"created_at":"2026-07-19T02:55:39.010633Z","pmid":"41824774","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":[]}