Effects of Negative Charges of a Model for Bovine Pancreatic Trypsin Inhibitor Folding Intermediate on the Peptide Folding

概要

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A peptide model (called PαPβ) of bovine pancreatic trypsin inhibitor (BPTI) for studying the peptide folding structure was designed as a crucial folding intermediate. The PαPβ model folded but it was unstable at low pH. Four acidic groups in PαPβ : Glu-49, Asp-50, and C-termini at Phe-33 and Ala-58, were replaced individually with an Ala (in case of Glu and Asp) and an amide group (for C-terminal carboxyl groups) to study the effects of these negative charged groups on folding structure in terms of thermal stability and pH dependence. Substituting the Glu-49 or Asp-50 with Ala and blocking the C-terminus carboxyl group of Phe-33 in Pβ destabilized the structure, but blocking the negative charge of C-terminus in Ala-58 of Pαstabilized the structure at neutral pH. These results can be interpreted in terms of helix dipole momentum effects and/or salt bridge formation between Asp-50 and Arg-53, and of electrostatic interaction between positive and negative charges, which stabilized the structure. The melting temperature of model peptides (T_m) in low ionic strength buffer were lower than that in high ionic strength buffer except the C-terminus blocking of Pα.
社団法人日本農芸化学会の論文
1994-02-23