SCIENCEADVANCES | RESEARCHARTICLE (grid.436923.9), a DOE O昀케ce of Science User Facility sponsored by the O昀케ce of Biological and depositedintheProteinDataBank(https://www.rcsb.org/)undertheaccessioncode8DWI.All Environmental Research. We also thank J. Kieft for the critical reading and suggestions. data needed to evaluate the conclusions in the paper are present in the paper and/or the Funding:ThisworkwassupportedbyNIH(R01GM126626,R21AG064572,R01HL133230,and Supplementary Materials. R01HL159086). Author contributions: W.H., C.C., K.S., and H.Z. designed the experiments, collectedandanalyzedthedata,andwrotethemanuscript.Competinginterests:Theauthors Submitted 11 September 2022 declare that they have no competing interests. Data and materials availability: The cryo-EM Accepted 16 December 2022 mapofSialin was deposited in the Electron Microscopy Data Bank (https://www.ebi.ac.uk/ Published 20 January 2023 emdb/) under the accession code EMD-27755. Coordinates of the atomic model were 10.1126/sciadv.ade8346 Huetal., Sci. Adv. 9, eade8346 (2023) 20 January 2023 9of9