Identification of the ice-binding face of a plant antifreeze protein.

The antifreeze protein of Lolium perenne, a perennial ryegrass, was previously modeled as a beta-roll with two extensive flat beta-sheets on opposite sides of the molecule. Here we have validated the model with a series of nine site-directed steric mutations in which outward-pointing short side-chain residues were replaced by tyrosine. None of these disrupted the fold.