2024-03-29T13:56:15Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/714372022-11-17T02:08:08Zhdl_2115_20055hdl_2115_8527Polypentagonal ice-like water networks emerge solely in an activity-improved variant of ice-binding proteinMahatabuddin, SheikhFukami, DaichiArai, TatsuyaNishimiya, YoshiyukiShimizu, RumiShibazaki, ChieKondo, HidemasaAdachi, MotoyasuTsuda, Sakaehydration shellice-binding proteincrystal structurewater clusterpolypentagonal waters430Polypentagonal water networks were recently observed in a protein capable of binding to ice crystals, or ice-binding protein (IBP). To examine such water networks and clarify their role in ice-binding, we determined X-ray crystal structures of a 65-residue defective isoform of a Zoarcidae-derived IBP (wild type, WT) and its five single mutants (A20L, A20G, A20T, A20V, and A20I). Polypentagonal water networks composed of similar to 50 semiclathrate waters were observed solely on the strongest A20I mutant, which appeared to include a tetrahedral water cluster exhibiting a perfect position match to the (1010) first prism plane of a single ice crystal. Inclusion of another symmetrical water cluster in the poly-pentagonal network showed a perfect complementarity to the waters constructing the (2021) pyramidal ice plane. The order of ice-binding strength was A20L < A20G < WT < A20T < A20V < A20I, where the top three mutants capable of binding to the first prism and the pyramidal ice planes commonly contained a bifurcated gamma-CH3 group. These results suggest that a fine-tuning of the surface of Zoarcidae-derived IBP assisted by a side-chain group regulates the holding property of its polypentagonal water network, the function of which is to freeze the host protein to specific ice planes.National Academy of Sciences.Journal Articleapplication/pdfhttp://hdl.handle.net/2115/71437https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/71437/1/5456.full.pdf0027-8424Proceedings of the National Academy of Sciences of the United States of America (PNAS)11521545654612018-05-22enginfo:pmid/29735675info:doi/10.1073/pnas.1800635115Copyright (C) 2018 the Author(s). Published by PNASpublisher