EN
Lanthanide-saturated peptides analogous to calcium-binding loops of EF-hand proteins can be used to stabilize the α-helical structure of peptide or protein segments attached to their C-termini. To study conformational properties of such loop-containing hybrids it is necessary to produce them in bacteria. In peptides obtained in this way the helix will be destabilized by the negatively charged C-terminal α-carboxyl groups. We propose to blocke them by the homoserine lactone. The results presented in this paper indicate that the presence of the lactone even at the C-terminus of the loop does not have any negative effect on the loop helix-nucleation ability. On the other hand, the presence of the α-NH+3 at the loop N-terminus leads to a drop of metal-binding constant and loss of the rigid structure of the α-helical segment of the loop. The α-amino group separated by one glycine residue from the loop N-terminus should also be avoided because it perturbs the conformation of the N-terminal part of the loop and may reduce the loop affinity to lanthanide ions.