Sequence determinants of thermodynamic stability in a WW domain--an all-beta-sheet protein.
The stabilities of 66 sequence variants of the human Pin1 WW domain have been determined by equilibrium thermal denaturation experiments. All 34 residues composing the hPin1 WW three-stranded beta-sheet structure could be replaced one at a time with at least one different natural or non-natural amino acid residue without leading to an unfolded protein. Alanine substitutions at only four positions within the hPin1 WW domain lead to a partially or completely unfolded protein-in the absence of a physiological ligand. The side chains of these four residues form a conserved, partially solvent-inaccessible, continuous hydrophobic minicore comprising the N- and C-termini. Ala mutations at five other residues, three of which constitute the ligand binding patch on the concave side of the beta-sheet, significantly destabilize the hPin1 WW domain without leading to an unfolded protein. The remaining mutations affect protein stability only slightly, suggesting that only a small subset of side chain interactions within the hPin1 WW domain are mandatory for acquiring and maintaining a stable, cooperatively folded beta-sheet structure.
Jäger
Marcus
M
Department of Chemistry and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Dendle
Maria
M
Kelly
Jeffery W
JW
D019943:Amino Acid Substitution / Q000502:physiology; D006801:Humans; D009154:Mutation; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D019696:Peptidylprolyl Isomerase / Q000737:chemistry* / Q000235:genetics; D017510:Protein Folding; D055550:Protein Stability; D017433:Protein Structure, Secondary / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D013816:Thermodynamics
D000072340:NIMA-Interacting Peptidylprolyl Isomerase; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase