Proton nuclear magnetic resonance analyses of the molecular conformations of unique long neurotoxins bearing Phe-25: Astrotia stokesii b, Astrotia stokesii c, and Acanthophis antarcticus b.
The 270-MHz proton NMR spectra of the unique long neurotoxins bearing Phe-25, Astrotia stokesii b (As b) and Astrotia stokesii c (As c) from Astrotia stokesii, and Acanthophis antarcticus b (Aa b) from Acanthophis antarcticus, have been analyzed. The aromatic proton resonances of Phe-25 in As b and Aa b were assigned on the basis of the nuclear Overhauser effects observed on irradiation of slowly exchanging amide protons. Phe-25 was found to be involved in hydrophobic interactions with Ile/Val-42, Ala-46 and Ile-58 in As b and As c, and with Ala-46 and Val-58 in Aa b. These hydrophobic interactions, instead of the hydrogen bond between Tyr-25 and Glu-42 found in other neurotoxins, appear to be important for maintenance of the biologically active tertiary structure. The pH dependency of the chemical shift and intensity of the Trp-72 N-1 proton resonance of As b indicates that the indole ring is not fully exposed to the solvent and that the extra tail segment of this long neurotoxin interacts with the main part of the molecule.
T
T
Endo
H S
HS
Kim
N
N
Maeda
N
N
Tamiya
T
T
Miyazawa
D002942:Circular Dichroism; D004546:Elapid Venoms; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009498:Neurotoxins; D010649:Phenylalanine; D014364:Tryptophan
D004546:Elapid Venoms; D009498:Neurotoxins; D010649:Phenylalanine; D014364:Tryptophan