Contribution of hydrophobic interactions to protein stability.
A major factor in the folding of proteins is the burying of hydrophobic side chains. A specific example is the packing of alpha-helices on beta-sheets by interdigitation of nonpolar side chains. The contributions of these interactions to the energetics of protein stability may be measured by simple protein engineering experiments. We have used site-directed mutagenesis to truncate hydrophobic side chains at an alpha-helix/beta-sheet interface in the small ribonuclease from Bacillus amyloliquefaciens (barnase). The decreases in stability of the mutant proteins were measured by their susceptibility to urea denaturation. Creation of a cavity the size of a -CH2-group destabilizes the enzyme by 1.1 kcal mol-1, and a cavity the size of three such groups by 4.0 kcal mol-1.
Kellis
J T
JT
Department of Chemistry, Imperial College of Science and Technology, London, UK.
Nyberg
K
K
Sali
D
D
Fersht
A R
AR
D001407:Bacillus / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D003460:Crystallization; D004795:Enzyme Stability; D006358:Hot Temperature; D008433:Mathematics; D009154:Mutation; D011487:Protein Conformation; D011489:Protein Denaturation; D011994:Recombinant Proteins / Q000235:genetics; D012260:Ribonucleases / Q000235:genetics; D014508:Urea / Q000378:metabolism
D001426:Bacterial Proteins; D011994:Recombinant Proteins; D014508:Urea; D012260:Ribonucleases; C019760:Bacillus amyloliquefaciens ribonuclease