Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 113, Issue 24, Pages 6683-6688Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1601519113
Keywords
insects; environmental stress; trehalose; crystallization; antifreeze protein
Categories
Funding
- National Institutes of Health [GM086249]
- NSF [EFRI-1332411]
- Howard Hughes Medical Institute
- National Center for Research Resources Grant [S10-RR025631]
- National Science Foundation (NSF) Chemistry Research Instrumentation and Facilities: Departmental Multiuser Instrumentation (CRIF:MU) award [CHE-0639094]
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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.
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