title: Antifreeze proteins govern the precipitation of trehalose in a freezing-avoiding insect at low temperature.
abstract: The remarkable adaptive strategies of insects to extreme environments are linked to the biochemical compounds in their body fluids. Trehalose, a versatile sugar molecule, can accumulate to high levels in freeze-tolerant and freeze-avoiding insects, functioning as a cryoprotectant and a supercooling agent. Antifreeze proteins (AFPs), known to protect organisms from freezing by lowering the freezing temperature and deferring the growth of ice, are present at high levels in some freeze-avoiding insects in winter, and yet, paradoxically are found in some freeze-tolerant insects. Here, we report a previously unidentified role for AFPs in effectively inhibiting trehalose precipitation in the hemolymph (or blood) of overwintering beetle larvae. We determine the trehalose level (29.6 ± 0.6 mg/mL) in the larval hemolymph of a beetle, Dendroides canadensis, and demonstrate that the hemolymph AFPs are crucial for inhibiting trehalose crystallization, whereas the presence of trehalose also enhances the antifreeze activity of AFPs. To dissect the molecular mechanism, we examine the molecular recognition between AFP and trehalose crystal interfaces using molecular dynamics simulations. The theory corroborates the experiments and shows preferential strong binding of the AFP to the fast growing surfaces of the sugar crystal. This newly uncovered role for AFPs may help explain the long-speculated role of AFPs in freeze-tolerant species. We propose that the presence of high levels of molecules important for survival but prone to precipitation in poikilotherms (their body temperature can vary considerably) needs a companion mechanism to prevent the precipitation and here present, to our knowledge, the first example. Such a combination of trehalose and AFPs also provides a novel approach for cold protection and for trehalose crystallization inhibition in industrial applications.
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Los Angeles, CA 90032; Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125; xwen3@calstatela.edu.
authors.forename: Xin
authors.initials: X
authors.lastname: Wen
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Los Angeles, CA 90032;
authors.forename: Sen
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556;
authors.forename: John G
authors.initials: JG
authors.lastname: Duman
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Los Angeles, CA 90032;
authors.forename: Josh Fnu
authors.initials: JF
authors.lastname: Arifin
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Los Angeles, CA 90032;
authors.forename: Vonny
authors.initials: V
authors.lastname: Juwita
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125;
authors.forename: William A
authors.initials: WA
authors.lastname: Goddard
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Los Angeles, CA 90032; Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125; Department of Physics and Astronomy, California State University, Los Angeles, CA 90032;
authors.forename: Alejandra
authors.initials: A
authors.lastname: Rios
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125;
authors.forename: Fan
authors.initials: F
authors.lastname: Liu
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125;
authors.forename: Soo-Kyung
authors.initials: SK
authors.lastname: Kim
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125;
authors.forename: Ravinder
authors.initials: R
authors.lastname: Abrol
authors.affiliation: Department of Animal Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801;
authors.forename: Arthur L
authors.initials: AL
authors.lastname: DeVries
authors.affiliation: Beckman Institute, California Institute of Technology, Pasadena, CA 91125.
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Henling
mesh_terms: D000818:Animals; D021301:Antifreeze Proteins / Q000737:chemistry* / Q000378:metabolism; D003080:Cold Temperature; D001517:Coleoptera / Q000737:chemistry* / Q000378:metabolism; D006458:Hemolymph / Q000737:chemistry* / Q000378:metabolism; D019476:Insect Proteins / Q000737:chemistry* / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D014199:Trehalose / Q000737:chemistry* / Q000378:metabolism
chemical_list: D021301:Antifreeze Proteins; D019476:Insect Proteins; D014199:Trehalose
keywords: antifreeze protein; crystallization; environmental stress; insects; trehalose