NMR conformational study of a model tetradecapeptide mimicking the RXVRG consensus cleavage site of a Xenopus laevis skin endoprotease.
A model tetradecapeptide, used for the purification of the RXVRG-endoprotease from Xenopus laevis skin exudate, has been studied by two-dimensional NMR, correlation (COSY) and NOE (NOESY) spectroscopy. This peptide has the 5-9 consensus sequence (RXVRG), along with an acidic moiety (1-4) and a hydrophobic domain (10-14). Variations with temperature of NH chemical shifts in a dimethyl sulfoxide solution (low thermal coefficients at residues 6, 7 and 8) and quantified NOE values from four spectra at different mixing times clearly showed a structural organization in the consensus domain with psi-angles around [-40, -10 degrees] for residues 7 and 8, and two NOE correlations of alpha HiNHi + 2 type (5-7 and 6-8). Moreover, a privileged rotamer in the side chain is established for three residues (Val2, Asp3 and Val7) and limited possibilities are discussed for seven others. Most of the folding trends were not observed in the [Ser7] derivative, underlying the relationship between the conformations and a full consensus sequence. In the model tetradecapeptide an equilibrium between two beta-turns of type I, fragments 4-7 and 5-8, seems the most probable. Comparison between this tetradecapeptide and its 4-14 fragment, also a substrate for RXVRG-endoprotease, shows that the 1-3 moiety (DVD) influences the consensus domain structure(s) and clearly stabilizes the folded one(s). Finally, two analytical methods are developed in order to determine: (1) the trifluoroacetic acid content of the peptide samples, on the basis of 19F NMR spectroscopy; (2) the mean phi- and psi-angles of each residue, from the whole set of NH/alpha H coupling constants (3JN alpha) and NOE data at a local level.
Chalaoux
F R
FR
LASIR, CNRS, Thiais, France.
Riand
J
J
Leseney
A M
AM
Baron
D
D
D000595:Amino Acid Sequence; D000818:Animals; D010450:Endopeptidases / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry*; D011487:Protein Conformation; D012867:Skin / Q000201:enzymology*; D013696:Temperature; D014982:Xenopus laevis
D009842:Oligopeptides; D010446:Peptide Fragments; D010450:Endopeptidases