An ice‐binding and tandem beta‐sandwich domain‐containing protein in Shewanella frigidimarina is a potential new type of ice adhesin

• Published in: The FEBS Journal
• Main Authors: Vance, Tyler D.R., Graham, Laurie A., Davies, Peter L.
• Other Authors: Canadian Institutes of Health Research
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2018
• Subjects: Antarc*; Antarctic
• Online Access: http://dx.doi.org/10.1111/febs.14424; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Ffebs.14424; https://onlinelibrary.wiley.com/doi/pdf/10.1111/febs.14424; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/febs.14424; https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/febs.14424

Out of the dozen different ice‐binding protein ( IBP ) structures known, the DUF 3494 domain is the most widespread, having been passed many times between prokaryotic and eukaryotic microorganisms by horizontal gene transfer. This ~25‐ kD a β‐solenoid domain with an adjacent parallel α‐helix is most commonly associated with an N‐terminal secretory signal peptide. However, examples of the DUF 3494 domain preceded by tandem Bacterial Immunoglobulin‐like ( BI g) domains are sometimes found, though uncharacterized. Here, we present one such protein ( Sf IBP _1) from the Antarctic bacterium Shewanella frigidimarina . We have confirmed and characterized the ice‐binding activity of its ice‐binding domain using thermal hysteresis measurements, fluorescent ice plane affinity analysis, and ice recrystallization inhibition assays. X‐ray crystallography was used to solve the structure of the Sf IBP _1 ice‐binding domain, to further characterize its ice‐binding surface and unique method of stabilizing or ‘capping’ the ends of the solenoid structure. The latter is formed from the interaction of two loops mediated by a combination of tandem prolines and electrostatic interactions. Furthermore, given their domain architecture and membrane association, we propose that these BI g‐containing DUF 3494 IBP s serve as ice‐binding adhesion proteins that are capable of adsorbing their host bacterium onto ice. Database Submitted new structure to the Protein Data Bank (PDB: 6BG8 ).