Conformation of an antigenic determinant for experimental autoimmune neuritis.

The conformation of SP-26, the synthetic peptide (residues 53-78) of myelin P2 protein that causes experimental autoimmune neuritis (EAN) in the peripheral nervous system, has been investigated in D2O using Fourier transform infra-red spectroscopy. Turns were found in 26% of the residues in the peptide, with rest of the residues in random coil (72%). The presence of 26% turns agrees well with the number of residues forming three turns in the antigenic region of the intact protein and the number of turns correlates well with the severity of EAN. Since turns also exist in peptides inducing experimental autoimmune encephalomyelitis, the central nervous system counterpart of EAN, turn structure may be a common structural motif for these closely related autoimmune neurological disorders.