Conformational study of the basic proline‐rich polypeptides from human parotid saliva

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Abstract
The conformational study of two basic proline‐rich polypeptides from human parotid saliva, P—D and P—E of known primary structures, was performed by CD and 1H—n.m.r. spectra measurements. These polypeptides contain consecutive sequences of five prolyl residues in their amino acid sequences. The troughs in CD spectra of P—D and P—E were found at 202 and 201 nm, respectively. These wavelengths were different from the value of 206 nm of poly‐l‐proline form II conformation. In spite of this, the existence of poly‐l‐proline form II conformation was suggested in the structure of P—D, because the trough for a fragmental peptide of P—D containing five consecutive prolyl residues was found at 204 nm. No remarkable change was detected in CD and 1H—n.m.r. spectra of P—D and P—E in the range of pH 3.0–11.0. The result suggests that no folding of polypeptide which might be affected by ionic interaction exists in its structure.