Histidyl tags and structural stabilization of linear peptides

Histidyl tags of variable length at the carboxy and amino termini of the ASYQDL sequence have been added. The hexapeptide has been chosen for its predicted low propensity to assume a preferred conformation in solution. The NMR data indicate the presence in solution of different folded conformations for two histidyl derivatives of the hexapeptide upon additions of the Ni(II) ion. Thus, presence of four or five histidines located at the extremities of an unfolded peptide seems not to be suitable for a structural ordering inducible by the metal ion to trigger specific biological functions.