Nuclear magnetic resonance study of the solution properties of the polypeptide neurotoxin I from the sea anemone Stichodactyla helianthus
- Univ. of New South Wales, Kensington (Australia)
The solution properties of the polypeptide neurotoxin I from the sea anemone Stichodactyla helianthus (Sh I) have been investigated by high-resolution H nuclear magnetic resonance (NMR) spectroscopy at 300 MHz. The pH dependence of the spectra has been examined over the range 1.1-12.2 at 27{degree}C. Individual pK{sub a} values have been obtained for the {alpha}-ammonium group of Ala-1 (8.6) and the side chains of Glu-8 (3.7), Tyr-36 (10.9), and Tyr-37 (10.8). For the remaining seven carboxyl groups in the molecule, four pK{sub a} values can be clearly identified. The five Lys residues titrate in the range 10.5-11, but individual pK{sub a} values could not be obtained because of peak overlap. Conformational changes associated with the protonation of carboxylates occur below pH 4, while in the alkaline pH range major unfolding occurs above pH 10. The molecule also unfolds at elevated temperatures. Exchange of the backbone amide protons has been monitored at various values of pH and temperature in the ranges pH 4-5 and 12-27{degree}C. Comparison of these properties of Sh I in solution with those of the related polypeptides anthopleurin A and Anemonia sulcata toxins I and II indicates that Sh I is less stable thermally and that there are some significant differences in the ionic interactions that maintain the tertiary structure. The solvent accessibility of aromatic residues has been probed with photochemically induced dynamic nuclear polarization NMR at 360 MHz.
- OSTI ID:
- 5599897
- Journal Information:
- Biochemistry; (USA), Vol. 28:4; ISSN 0006-2960
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
POLYPEPTIDES
CONFORMATIONAL CHANGES
TOXINS
NUCLEAR MAGNETIC RESONANCE
AQUEOUS SOLUTIONS
CHEMICAL SHIFT
MOLLUSCS
NMR SPECTRA
PROTONS
TYROSINE
AMINO ACIDS
ANIMALS
ANTIGENS
AQUATIC ORGANISMS
BARYONS
CARBOXYLIC ACIDS
DISPERSIONS
ELEMENTARY PARTICLES
FERMIONS
HADRONS
HYDROXY ACIDS
INVERTEBRATES
MAGNETIC RESONANCE
MATERIALS
MIXTURES
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PEPTIDES
PROTEINS
RESONANCE
SOLUTIONS
SPECTRA
TOXIC MATERIALS
550601* - Medicine- Unsealed Radionuclides in Diagnostics