The dynamics and binding of a Type III antifreeze protein in water and on ice

Certain plants, insects and fish living in cold environments prevent tissue damage from freezing by producing antifreeze proteins or antifreeze glycoproteins [1]. These proteins work by inhibiting ice growth below the normal equilibrium freezing point of water. Fish antifreeze proteins are categorized into helical Type I AFPs, cysteine rich globular Type II AFPs, and small globular Type III AFPs. A three dimensional structure of Type III antifreeze protein was determined recently by NMR spectroscopy [2]. Using this solution structure we performed a 110 ps molecular dynamics simulation in a 50 x 50 x 50 Angstrom box of TIP3P water. Structural, dynamical and protein-water interactions during the simulation were investigated and are reported in this article. In addition, the dynamics structure was used to investigate possible protein-ice binding interactions. In particular, the protein face proposed by Chao et al. [3] was modeled on the (100) ice face and is discussed in terms of protein-ice interactions.