Double Duty For Eggshell Protein

Eggshells are chemical fortresses for developing animals—they protect against mechanical stress and bacterial invaders. Now, an international team led by Suresh Valiyaveettil of the National University of Singapore demonstrates how a key protein in turtle eggshells helps perform those tasks (J. Am. Chem. Soc., DOI: 10.1021/ja075659k). Generally, eggshells are made from a protein matrix with a buildup of calcium mineral crystals, and the varying mineral composition determines how stiff the eggshell is. The team determined the NMR structure of pelovaterin, a 42-amino-acid peptide from pliable eggshells laid by Chinese soft-shelled turtles. They found that pelovaterin resembles antimicrobial peptides from mammals and that it kills some bacteria in vitro. The team also found that pelovaterin aggregates into nanospheres, which influence the crystal form of calcium carbonate deposits. Because calcium carbonate crystallizes in different forms in different animal eggshells, learning how biological templates such as pelovaterin influence inorganic mineral growth could be helpful for producing better materials.