Crystal waters on the nine polyproline type II helical bundle springtail antifreeze protein from Granisotoma rainieri match the ice lattice. (3rd February 2021)

• Record Type: Journal Article
• Authors: Scholl, Connor L.; Tsuda, Sakae; Graham, Laurie A.; Davies, Peter L.
• Is Part Of: FEBS journal. Volume 288:Number 14(2021)
• Page Start: 4332
• Page End: 4347
• Publication Date: 2021-02-03
• Subjects: antifreeze protein -- bound waters -- Collembola -- ice lattice -- X‐ray crystallography; Biochemistry -- Periodicals; Molecular biology -- Periodicals; Pathology, Molecular -- Periodicals; 572
• DOI: 10.1111/febs.15717
• Languages: English
• ISSNs: 1742-464X

Abstract

Abstract : A springtail (Collembola) identified as Granisotoma rainieri was collected from snow in Hokkaido, Japan, in late winter when nighttime temperatures were below zero. Extracts of these arthropods showed antifreeze activity by shaping ice crystals and stopping their growth. The glycine‐rich proteins responsible for this freezing point depression were isolated by ice‐affinity purification and had principal masses of ~ 6.9 and 9.6 kDa. We identified a transcript for a 9.6‐kDa component and produced it as a His‐tagged recombinant protein for structural analysis. Its crystal structure was solved to a resolution of 1.21 Å and revealed a polyproline type II helical bundle, similar to the six‐helix Hypogastrura harveyi AFP, but with nine helices organized into two layers held together by an extensive network of hydrogen bonds. One of the layers is flat, regular, and hydrophobic and likely serves as the ice‐binding side. Although this surface makes close protein–protein contacts with its symmetry mate in the crystal, it has bound chains of waters present that resemble those on the basal and primary prism planes of ice. Molecular dynamic simulations indicate most of these crystal waters would preferentially occupy these sites if exposed to bulk solvent in the absence of the symmetry mate. These prepositioned waters lend further support to the ice‐binding mechanism in which AFPs organize ice‐like waters on one surface to adsorb to ice. Databases: Structural data are available in the Protein Data Bank under the accession number 7JJV . Transcript data are available in GenBank under accession numbers MT780727, MT780728, MT780729, MT780730, MT780731 and MT985982. Abstract : The springtail Granisotoma rainieri collected in Sapporo, Japan, can survive subzero temperatures by producing antifreeze proteins (AFP), which circulate in the springtail and prevent ice crystals from growing larger. The 9.6‐kDa AFP was recombinantly produced for structural analysis. Its crystal structure (bottom) was solved to a resolution of 1.21Å and revealed a polyproline type II helical bundle with nine helices organized into two layers.