Siemion I Z, Pedyczak A, Burton J
Institute of Chemistry, Wrocław University, Poland.
Biophys Chem. 1988 Aug;31(1-2):35-44. doi: 10.1016/0301-4622(88)80006-1.
The mean solution conformation of tetrapeptide fragments spanning the hinge region of human IgA1 was investigated by CD and 13C-NMR methods. Distinct conformational differences for the partial sequences of IgA1 were found. In a series of tetrapeptides having the Thr-Pro-Pro-Thr sequence, the Pro-Pro fragment was ordered to the structure of a type II polyproline helix, but with unordered forms prevailing in the equilibria. In the case of the Pro-Pro-Thr-Pro sequence, a distinct preference for the beta-turn conformation was found. Acetylation of this tetrapeptide shifts the equilibrium towards unordered forms containing some elements of the type II polyproline helix. The peptide Thr-Pro-Ser-Pro exists predominantly in the beta-turn conformation whereas Pro-Ser-Pro-Ser-NH2 has, for the most part an unordered conformation.
