[Determination of the secondary structure of proteins from their circular dichroism spectra. II. Estimation of the contribution of beta-pleated sheets].

Protein-derived basic CD spectra for alpha-helical, beta-structural, beta-bends and irregular regions of the proteins have been determined from the experimental CD spectra of five reference proteins (myoglobin, lysozyme, ribonuclease A, papain, lactate dehydrogenase) with the knowledge of the fractions of the residues in the corresponding conformation. The alpha-helical and beta-structural regions of the reference proteins have been isolated from the X-ray data using the common "rigid" criteria for all the proteins, as proposed by Finkelstein and Ptitsyn. The residues in the beta-bend have been isolated using the data of Chou and Fasman and also three assumptions formulated in the present paper. The basic CD spectra thus obtained have been used for the analysis of secondary structures of 10 proteins (5 reference and 5 additional ones). There is a good agreement between the results of the X-ray data and those obtained from the CD spectra.