P2.195  Monday, Jan. 5  Modeling ice-binding motifs in antifreeze proteins from the Alaskan beetle Cucujus clavipes puniceus SFORMO, T*; BARNES, B; DUMAN, J; SCHULTE, M; Univ. Alaska Fairbanks; Univ. Alaska Fairbanks; Univ. of Notre Dame; Univ. Alaska Fairbanks rfts@uaf.edu

The freeze-avoiding beetle larvae Cucujus clavipes puniceus overwinters in Alaska under the bark of decaying trees. These larvae are intermittently exposed to ambient winter temperatures as low as -45C in situ and readily supercool to -35 to -55C; under experimental conditions, some larvae do not freeze even when cooled to -100C and enter a vitrified state between -58 to -85C. We modeled C. c. puniceus antifreeze proteins (AFPs) using Sybyl molecular modeling software (7.1 and 8.0, Tripos, Ltd.) to compare sequence, model structure, and visualize putative ice-binding motifs. We found that the AFPs are similar to AFPs from the beetle Tenebrio molitor. The C. c. puniceus AFPs are 7.6 to 8.3 kDa molecules that are threonine(Thr)- and cysteine (Cys)-rich. Each molecule is composed of six loops of 12 amino acids, and most loops have a regular array of Thr-Cys-Thr, with Cys internally disulfide bridged. We also show that the spacing of Thr is approximately aligned to both ice prism and basal planes, forming the putative ice-binding face. Stability of supercooling and vitrification in Cucujus may be enhanced by AFPs, as well as desiccation and synthesis of cryoprotectants. NSF #0618436