Structural and genetic analysis of protein stability.

One very encouraging development has been the freedom with which amino acid replacements can be introduced in a protein of interest. This has made it possible to obtain detailed structural and thermodynamic data on a wide variety of mutants that modify protein stability. Substitutions of solvent-exposed amino acids on the surfaces of proteins are seen to have little if any effect on protein stability or structure, leading to the view that it is the rigid parts of proteins that are critical for folding and stability. There is every reason to expect that it will be possible to rationalize the stabilities of mutant proteins from accurate knowledge of their structures. Substantial progress is being made in quantitating the interactions that determine and stabilize protein structures. Although not specifically the subject of this review, substantial progress is also being made in developing methods to engineer proteins of enhanced stability.