Chapter 22.3 Hydrogen bonding in biological macromolecules

Hydrogen bonds are weak non-covalent interactions, but their directional nature and the large number of hydrogen-bonding groups mean that they play a critical role in the structure and function of proteins and nucleic acids. Analyses of three-dimensional structures, particularly of proteins, reveal many consistent patterns, which are described in this review. Protein structures show almost complete saturation of hydrogen-bonding potential. Helices, β-strands, β-turns and γ-turns all show characteristic C=O···HN geometries, with helices having a variety of termination patterns. Local interactions are very common for main-chain···side-chain hydrogen bonds and may help direct protein folding. Non-local interactions, although fewer in number, can be very important for structural stability, and bound water molecules, because of their double-donor, double-acceptor capability, can play critical roles in satisfying overall hydrogen-bonding requirements. Finally, there is also a growing realization that non-conventional hydrogen bonds may play a more important role than hitherto recognized. Keywords: beta-sheets; amino-aromatic hydrogen bonding; DNA; helices; hydrogen bonding; hydrogen-bonding criteria; hydrogen-bonding potential; nucleic acids; protein folding; protein stability; RNA; secondary structure; side-chain hydrogen bonding; turns