Water and cellular folding processes.

Proteins require a unique, native structure to perform their functions. Water molecules play an important role to develop and maintain this three-dimensional structure. Water is also necessary for several forms of enzyme catalysis, and is a constituent of many protein-protein, protein-DNA, or protein-RNA interfaces. Larger proteins acquire their native structure in a complicated folding pathway having several folding traps. Recent data indicated a key role of water molecules in this process. Protein flexibility, structural rearrangements, conformational transitions all require the fluctuating changes in hydrogen bond structure provided by interacting water molecules. Besides proteins, RNA and DNA structure is also heavily influenced by the presence of water. This review summarizes the important aspects of these fields, and draws attention to several open questions and hypotheses.