[Secondary structure of polypeptide hormones of the anterior lobe of the pituitary gland].
The specificity of the secondary structure of a number of polypeptide hormones of the pituitary gland anterior lobe and their fragments were studied by circular dichroism method in the peptide bond absorption region and infrared spectroscopy. The state of objects had been examined in solvents of different polarity in a wide temperature range. The polypeptide chain of a greater part of hormones in aqueous solution is shown to represent a left-handed helix of the poly-L-proline II type. The reversible melting process of the left-handed conformation when heated in aqueous solution appears to be non-cooperative: delta epsilon is linearly dependent on temperature. Upon temperature lowering the left-handed structure is stabilized, its defects decrease. The mode of transition from the left-handed form to the alpha- and the beta-forms in organic solvents was followed. Contributions of peptide chromophores and those of aromatic amino acid side group chromophores with circular dichroism bands in regions under study were differentiated upon analysis of circular dichroism spectra. The data obtained allow to correlate conformation of separate fragments in the hormone chain with functional activity.
D000818:Animals; D002942:Circular Dichroism; D010908:Pituitary Hormones, Anterior; D011487:Protein Conformation; D012997:Solvents; D013552:Swine; D013696:Temperature
D010908:Pituitary Hormones, Anterior; D012997:Solvents
Vtorichnaia struktura polipeptidnykh gormonov peredneĭ doli gipofiza.