title: Ice-binding proteins that accumulate on different ice crystal planes produce distinct thermal hysteresis dynamics.
abstract: Ice-binding proteins that aid the survival of freeze-avoiding, cold-adapted organisms by inhibiting the growth of endogenous ice crystals are called antifreeze proteins (AFPs). The binding of AFPs to ice causes a separation between the melting point and the freezing point of the ice crystal (thermal hysteresis, TH). TH produced by hyperactive AFPs is an order of magnitude higher than that produced by a typical fish AFP. The basis for this difference in activity remains unclear. Here, we have compared the time dependence of TH activity for both hyperactive and moderately active AFPs using a custom-made nanolitre osmometer and a novel microfluidics system. We found that the TH activities of hyperactive AFPs were time-dependent, and that the TH activity of a moderate AFP was almost insensitive to time. Fluorescence microscopy measurement revealed that despite their higher TH activity, hyperactive AFPs from two insects (moth and beetle) took far longer to accumulate on the ice surface than did a moderately active fish AFP. An ice-binding protein from a bacterium that functions as an ice adhesin rather than as an antifreeze had intermediate TH properties. Nevertheless, the accumulation of this ice adhesion protein and the two hyperactive AFPs on the basal plane of ice is distinct and extensive, but not detectable for moderately active AFPs. Basal ice plane binding is the distinguishing feature of antifreeze hyperactivity, which is not strictly needed in fish that require only approximately 1°C of TH. Here, we found a correlation between the accumulation kinetics of the hyperactive AFP at the basal plane and the time sensitivity of the measured TH.
authors.affiliation: Institute of Biochemistry, Food Science and Nutrition, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
authors.forename: Ran
authors.identifier: http://orcid.org/https://orcid.org/0000-0002-6436-5602
authors.initials: R
authors.lastname: Drori
authors.affiliation: Department of Physics and Astronomy, Ohio University, Athens, OH, USA.
authors.forename: Yeliz
authors.initials: Y
authors.lastname: Celik
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada.
authors.forename: Peter L
authors.initials: PL
authors.lastname: Davies
authors.affiliation: Institute of Biochemistry, Food Science and Nutrition, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel Department of Physics and Astronomy, Ohio University, Athens, OH, USA ido.braslavsky@mail.huji.ac.il.
authors.forename: Ido
authors.identifier: http://orcid.org/https://orcid.org/0000-0001-8985-8211
authors.initials: I
authors.lastname: Braslavsky
mesh_terms: D021301:Antifreeze Proteins / Q000737:chemistry*; D003460:Crystallization; D004220:Disulfides / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry; D005615:Freezing; D049452:Green Fluorescent Proteins / Q000737:chemistry; D007053:Ice; D053544:Marinomonas / Q000737:chemistry; D046210:Microfluidic Analytical Techniques; D044085:Microfluidics; D008856:Microscopy, Fluorescence; D011485:Protein Binding; D012984:Software
chemical_list: D021301:Antifreeze Proteins; D004220:Disulfides; D007053:Ice; D049452:Green Fluorescent Proteins
keywords: antifreeze proteins; ice-binding; thermal hysteresis