title: Distributions of water around amino acid residues in proteins.
abstract: The atomic co-ordinates from 16 high-resolution (less than or equal to 1.7 A = 0.1 nm), non-homologous proteins have been used to study the distributions of water molecule sites around the 20 different amino acid residues. The proportion of residues whose main-chain atoms are in contact with water molecules was fairly constant (between 40% and 60%), irrespective of the nature of the side-chain. However, the proportion of residues whose side-chain atoms were in contact with water molecules showed a clear (inverse) correlation with the hydrophobicity of the residue, being as low as 14% for leucine and isoleucine but greater than 80% for asparagine and arginine. Despite the problems in determining accurate water molecule sites from X-ray diffraction data and the complexity of the protein surface, distinct non-random distributions of water molecules were found. These hydration patterns are consistent with the expected stereochemistry of the potential hydrogen-bonding sites on the polar side-chains. The water molecules around apolar side-chains lie predominantly at van der Waals' contact distances, but most of these have a primary, shorter contact with a neighbouring polar atom. Further analysis of these distributions, combined with energy minimization techniques, should lead to improved modelling of protein structures, including their primary shells of hydration.
authors.affiliation: Department of Crystallography, Birkbeck College, University of London, U.K.
authors.forename: N
authors.initials: N
authors.lastname: Thanki
authors.forename: J M
authors.initials: JM
authors.lastname: Thornton
authors.forename: J M
authors.initials: JM
authors.lastname: Goodfellow
mesh_terms: D000595:Amino Acid Sequence; D006860:Hydrogen Bonding; D008969:Molecular Sequence Data; D011506:Proteins; D014867:Water; D014961:X-Ray Diffraction
chemical_list: D011506:Proteins; D014867:Water