A CYCLIC DISULFIDE PEPTIDE REPRODUCES IN SOLUTION THE MAIN STRUCTURALFEATURES OF A NATIVE ANTIGENIC SITE OF FOOT-AND-MOUTH-DISEASE VIRUS

A cyclic disulfide peptide corresponding to the G-H loop sequence 134- 155 [replacement Tyr136 and Arg153 with Cys] of the capsid protein VP1 of foot-and-mouth disease virus (FMDV) isolate C-S8c1 was examined by proton 2D-NMR spectroscopy in water and in 25% HFIP/water. In water, NMR data supported the presence of a non-canonical turn in the central , conserved cell adhesion RGD motif and suggested the presence of a na scent helix in the C-terminal part, stabilized and slightly extended u pon addition of 25% HFIP, a secondary structure stabilizing cosolvent. The formation of the C-terminal helix was evidenced by combined analy sis of NOE connectivities, H alpha chemical shifts, (3)J(NH-H alpha) c oupling constants and amide temperature coefficients. Surprisingly, th ese global structural features of the cyclic peptide in solution show similarities to previous X-ray structure analysis of (a) a shortened l inear peptide complexed with a antivirus antibody and (b) the G-H loop represented on the chemical reduced viral surface of a different sero type. Thus, even in entirely different biological environments the cyc lic peptide reflect similar structural features, reinforcing the conce pt that this viral loop behaves as an independent structural and funct ional unit. (C) 1997 Elsevier Science B.V.