Guidelines for Protein Design: The Energetics of β Sheet Side Chain Interactions

To determine the interaction energy between cross-strand pairs of side chains on an antiparallel β sheet, pairwise amino acid substitutions were made on the solvent-exposed face of the B1 domain of streptococcal protein G. The measured interaction energies were substantial (1.8 kilocalories per mole) and comparable to the magnitude of the β sheet propensities. The experimental results paralleled the statistical frequency with which the residue pairs are found in β sheets of known structure.