Antifreeze proteins can be found in a variety of organisms that get exposed to below freezing temperatures. These proteins are essential to prevent large ice crystal growth and damage to the cells of the organism. One theory regarding the mechanism by which these proteins prevent the growth of ice crystals is through structuring of water molecules at the ice-water interface to form “clathrate-like” cages. However, there are other alternate proposed mechanisms, and the precise cause of their ice inhibition activity is not well understood. There are several different types of antifreeze proteins, with one of them being classified as Type IV. Type IV antifreeze proteins have no discernible sequence homologies or conserved residues but share structural homology and are composed of three helix bundles. Unlike Type I antifreeze proteins found in fish, there are no repeats of amino acid sequences and thus the mechanism of ice-binding and freeze resistance is likely to be significantly different. To better characterize the mechanism of the antifreeze activity of type IV AFPs, the gene for a Type IV protein from Antarctobacter heliothermus was incorporated into a plasmid and transformed into E. coli BL21(DE3) competent cells. Proper protocols were tested and determined to optimize protein expression of the target protein in E. coli. Future work will focus on the biophysical characterization of this protein, testing its antifreeze activity, and determining its structure activity relationships.

Expression of a type IV antifreeze protein from Antarctobacter heliothermus in E. coli

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