Conformation of an octapeptide fragment (2-9) of kaliocin-1 in DMSO-d6 by 1H NMR and restrained molecular dynamics.

Kaliocin-1, a 31-residue synthetic peptide (FFSASCVPGADKGQFPNLCRLCA GTGENKCA), which has shown the antimicrobial activity forms the 152-182 fragment of human lactoferrin (HLf). As the octapeptide FSASCVPG forms the 2-9 fragment of kaliocin-1, in the present study, its conformation in dimethyl sulfoxide-d6 (DMSO-d6) has been determined using two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy as well as restrained molecular dynamics. Sequence specific assignments of all the 1H resonances have been carried out using 2D correlation experiments (2D DQF-COSY, TOCSY and ROESY). In dimethyl sulfoxide-d6 at 25 degrees C, the octapeptide adopts a predominantly extended backbone conformation. The calculated structure resembles closely with the reported structure of the corresponding fragment of HLf. The peptide also has sequence and structural similarity with the corresponding fragments of lactoferrins from other organisms.