title: Structure-based thermodynamic scale of alpha-helix propensities in amino acids.
abstract: A structural parameterization of the folding energetics has been used to predict the effect of single amino acid mutations at exposed locations in alpha-helices. The results have been used to derive a structure-based thermodynamic scale of alpha-helix propensities for amino acids. The structure-based thermodynamic analysis was performed for four different systems for which structural and experimental thermodynamic data are available: T4 lysozyme [Blaber et al (1994) J. Mol. Biol.235, 600-624], barnase [Horovitz et al. (1992) J.Mol.Biol.227,560-568], a synthetic leucine zipper [O'Neil & Degrado (1990) Science 250, 646-651], and a synthetic peptide [Lyu et al. (1990) Science 250, 669-673]. These studies have permitted the optimization of the set of solvent-accessible surface areas (ASA) for all amino acids in the unfolded state. It is shown that a single set of structure/thermodynamic parameters accounts well for all the experimental data sets of helix propensities. For T4 lysozyme, the average value of the absolute difference between predicted and experimental delta G values is 0.09 kcal/mol, for barnase 0.14 kcal/mol, for the synthetic coiled-coil 0.11 kcal/mol, and for the synthetic peptide 0.08 kcal/mol. In addition, this approach predicts well the overall stability of the proteins and rationalizes the differences in alpha-helix propensities between amino acids. The excellent agreement observed between predicted and experimental delta G values for all amino acids validates the use of this structural parameterization in free energy calculations for folding or binding.
authors.affiliation: Department of Biology and Biocalorimetry Center, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: I
authors.initials: I
authors.lastname: Luque
authors.forename: O L
authors.initials: OL
authors.lastname: Mayorga
authors.forename: E
authors.initials: E
authors.lastname: Freire
mesh_terms: D000596:Amino Acids / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins; D016350:Leucine Zippers; D009113:Muramidase / Q000737:chemistry; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D012044:Regression Analysis; D012260:Ribonucleases / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D010455:Peptides; D011506:Proteins; D012260:Ribonucleases; C019760:Bacillus amyloliquefaciens ribonuclease; D009113:Muramidase