SIMULATIONS OF CONFORMERS OF TUFTSIN AND A CYCLIC TUFTSIN ANALOG

The conformational properties of the configurational isomers of tuftsi n, a linear tetrapeptide with the sequence Thr-Lys-Pro-Arg, were inves tigated with six 1 ns molecular dynamics simulations in explicit water and in a 1.0 M NaCl solution. The average conformation of the cis iso mer is a type VI beta-turn. Our results indicate that water-peptide hy drogen bonding, in addition to intramolecular hydrogen bonds, stabiliz es the cis conformer, The trans isomer is neither a beta- nor a gamma- turn. Results are compared with parallel studies on a cyclic analog of tuftsin, cyclo (Thr-Lys-Pro-Arg-Gly). The addition of salt does not i nfluence the backbone conformation of the peptide. Differences between the structures are confined to the side-chain orientations of the Lys and Arg residues. (C) Munksgaard 1995.