C-terminal secretion signal of an Erwinia chrysanthemi protease secreted by a signal peptide-independent pathway: proton NMR and CD conformational studies in membrane-mimetic environments.
Wolff N. | Ghigo J.M. | Delepelaire P. | Wandersman C. | Delepierre M.
The detailed structure of a 68-residue chimeric peptide encompassing the 56 last C-terminal residues of Erwinia chrysanthemi protease G has been investigated by using circular dichroism and NMR spectroscopies. The peptide which contains the secretion signal of PrtG was solubilized either in aqueous solvent, in trifluoroethanol (TFE)/H2O mixtures, or in dodecyl beta-D-maltoside detergent. The peptide helical content increases upon TFE and detergent additions. A stable conformation is reached at 40% TFE (v:v) and at a micelle to peptide ratio higher than 1. The 1H NMR spectrum has been assigned in TFE/ H2O, 2:1 (v:v), and it is shown that residues 26-29 and 50-62 form a relatively stable helix although a conformational equilibrium between a helix and probably a more random structure is observed throughout fragment 13-63. Comparison of the C-terminal conformation with results obtained by deletion approach could lead to the hypothesis that the C-terminal secretion signal is composed of an alpha-helix located close to the essential C-terminal tetrapeptide.
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