The helical s constant for alanine in water derived from template-nucleated helices

FORMATION of α helices from disordered polypeptides depends on the degree to which amino acids favour the helical state. The folding of helical oligopeptides can be modelled by two parameters: σ which reflects helix initiation and s which reflects propagation of a pre-existing helix and measures helical bias1,2. Scheraga has reported s values for oligopeptides of about 1.1, implying a weak helical bias for amino-acid residues3. By contrast, certain helical peptides studied by Baldwin seem to require much larger s values for alanine4. Resolution of this inconsistency requires experiments that disentangle the ease of propagation from that of initiation. In this study varying lengths of polyalanine are linked to a 'template' that initiates helical structure and permits study solely of propagation. We report here that the s value for alanine in water is close to 1, supporting the earlier results of Scheraga but not the more recent results of Baldwin.

[1]  D. States,et al.  A two-dimensional nuclear overhauser experiment with pure absorption phase in four quadrants☆ , 1982 .

[2]  P E Wright,et al.  Folding of immunogenic peptide fragments of proteins in water solution. II. The nascent helix. , 1988, Journal of molecular biology.

[3]  P E Wright,et al.  Folding of immunogenic peptide fragments of proteins in water solution. I. Sequence requirements for the formation of a reverse turn. , 1988, Journal of molecular biology.

[4]  Structure determination of a tetrasaccharide: transient nuclear Overhauser effects in the rotating frame , 1984 .

[5]  M. Illangasekare,et al.  Circular dichroism studies of distorted α-helices, twisted β-sheets, and β-turns , 1988 .

[6]  P. S. Kim,et al.  A salt bridge stabilizes the helix formed by isolated C-peptide of RNase A. , 1982, Proceedings of the National Academy of Sciences of the United States of America.

[7]  R. L. Baldwin,et al.  Unusually stable helix formation in short alanine-based peptides. , 1989, Proceedings of the National Academy of Sciences of the United States of America.

[8]  M. Billeter,et al.  Calibration of the angular dependence of the amide proton-Cα proton coupling constants, 3JHNα, in a globular protein: Use of 3JHNα for identification of helical secondary structure , 1984 .

[9]  Kurt Wüthrich,et al.  1H‐nmr parameters of the common amino acid residues measured in aqueous solutions of the linear tetrapeptides H‐Gly‐Gly‐X‐L‐Ala‐OH , 1979 .

[10]  R. R. Ernst,et al.  Separation of cross-relaxation and J cross-peaks in 2D rotating-frame NMR spectroscopy , 1987 .

[11]  J. Flippen-Anderson,et al.  Conformation of a 16-residue zervamicin IIA analog peptide containing three different structural features: 3(10)-helix, alpha-helix, and beta-bend ribbon. , 1987, Proceedings of the National Academy of Sciences of the United States of America.

[12]  K Wüthrich,et al.  Polypeptide secondary structure determination by nuclear magnetic resonance observation of short proton-proton distances. , 1984, Journal of molecular biology.

[13]  B. Zimm,et al.  Theory of the Phase Transition between Helix and Random Coil in Polypeptide Chains , 1959 .

[14]  A. Pardi,et al.  Hydrogen bond length and proton NMR chemical shifts in proteins , 1983 .

[15]  Douglas Poland,et al.  Theory of helix-coil transitions in biopolymers , 1970 .

[16]  I. Campbell,et al.  High-resolution 1H NMR study of the solution structure of alamethicin. , 1987, Biochemistry.

[17]  H. Scheraga.  Use of random copolymers to determine the helix-coil stability constants of the naturally occurring amino acids , 1978 .

[18]  D. Kemp,et al.  (2S,5S,8S,11S)-1-Acetyl-1,4-diaza-3-keto-5-carboxy-10-thia-tricyclo-[2.8.04,8]-tridecane, 1 synthesis of prolyl-proline-derived, peptide-functionalized templates for α-helix formation , 1988 .

[19]  D. G. Davis,et al.  Practical aspects of two-dimensional transverse NOE spectroscopy , 1985 .