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A helix propensity scale based on experimental studies of peptides and proteins
Journal article   Open access   Peer reviewed

A helix propensity scale based on experimental studies of peptides and proteins

C N Pace and J M Scholtz
Biophysical journal, Vol.75(1), pp.422-427
07/01/1998
DOI: 10.1016/S0006-3495(98)77529-0
PMCID: PMC1299714
PMID: 9649402
url
https://doi.org/10.1016/S0006-3495(98)77529-0View
Published (Version of record) Open Access

Abstract

The average globular protein contains 30% alpha-helix, the most common type of secondary structure. Some amino acids occur more frequently in alpha-helices than others; this tendency is known as helix propensity. Here we derive a helix propensity scale for solvent-exposed residues in the middle positions of alpha-helices. The scale is based on measurements of helix propensity in 11 systems, including both proteins and peptides. Alanine has the highest helix propensity, and, excluding proline, glycine has the lowest, approximately 1 kcal/mol less favorable than alanine. Based on our analysis, the helix propensities of the amino acids are as follows (kcal/mol): Ala = 0, Leu = 0.21, Arg = 0.21, Met = 0.24, Lys = 0.26, Gln = 0.39, Glu = 0.40, Ile = 0.41, Trp = 0.49, Ser = 0.50, Tyr = 0. 53, Phe = 0.54, Val = 0.61, His = 0.61, Asn = 0.65, Thr = 0.66, Cys = 0.68, Asp = 0.69, and Gly = 1.

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