Hydrogen-bonds in protein secondary and tertiary structures

6^th March 2025, 14:00
Zygmunt Derewenda
University of Virginia, US

Abstract

Proteins are linear polymers linked by peptide bonds. The partial double bond character on the N-C linkage polarizes the N-H and C=O groups so that partial positive and negative charges form there, respectively. This property allows both groups to be involved in hydrogen bonds (H-bonds)and donors and acceptors, respectively. It has been hypothesized early on, that if two such polymers lie side-by-side, alternative N-H…O=C and C=O…H-N bonds can form between the main chains of these molecules. In the 1950s, Linus Pauling formally described an atomic model of such a ?-sheet, along with the structures of the ?, ? and 310 helices, in which the polypeptide chains twists in a helical manner and locks into stable stereochemistry when H-bonds form between 1?3, 1?4 and 1?5 amino acids. Interestingly, because naturally occurring amino acids are D-stereoisomers, stable helices are normally right-handed. However, rare examples of left-handed helices do occur in nature as well. When protein structures were finally visualized by X-ray crystallography, the presence of all these elements was experimentally confirmed. Moreover, a variety of additional recurring motifs were discovered, such as turns, helix breaks, caps, etc. It became also clear that groups such as C?-H can serve as donors, while aromatic rings such as are found in phenylalanine, tyrosine and tryptophan, can play a role of acceptors. My presentation will provide an overview of the role of H-bonds in protein secondary and tertiary structures.