Hyperactive antifreeze proteins

AFPs occur naturally in many fish, insects, plants, and other organisms, allowing them to survive sub-freezing temperatures. The proteins come in various forms, but all seem to act similarly—they bind to nascent ice crystals and inhibit the crystals’ subsequent growth, which effectively reduces the freezing point of ice in the organism. The AFP that is found in the spruce budworm (sbw) seems to be hyperactive and especially effective at protecting its host in the frigid winters of the northern US and Canada. A US–Canada team led by physicist Ido Braslavsky (Ohio University) and biochemist Peter Davies (Queen’s University) marked sbwAFP with green fluorescent protein and with the help of fluorescence microscopy observed how the hyperactive protein coated the basal planes of ice crystals, halting their growth out of that plane. Previously the researchers had studied fluorescently tagged fish AFP types I and III. In this confocal microscopy image, it is apparent that the marked hyperactive sbwAFP (appears green) has accumulated on several surfaces of the ice crystals, including the basal planes, while the fish AFP type I (appears red) is mainly still in solution. Natural, nontoxic AFPs have many current and potential applications in the medical, agricultural, and food industries. Braslavsky reported the work at the March 2007 APS meeting in Denver. (N. Pertaya et al., paper J35.8. For the fish AFP type III work, see N. Pertaya et al., Biophys. J. 92 , 3663, 2007 http://dx.doi.org/10.1529/biophysj.106.096297 .)