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Solution structure of Pi4, a four disulfide bridged scorpion toxin active on potassium channels
SOLUTION NMR
NMR Experiment
Experiment
Type
Sample Contents
Solvent
Ionic Strength
pH
Pressure
Temperature (K)
Spectrometer
1
2D NOESY
2.5 mM Pi4, 5 mM CD3COONa, pH 4.0, 10% D2O
90% H2O/10% D2O
5
4.0
ambient
303
2
P-COSY
2.5 mM Pi4, 5 mM CD3COONa, pH 4.0, 10% D2O
90% H2O/10% D2O
5
4.0
ambient
303
3
2D NOESY
3.2 mM Pi4, 5 mM CD3COONa, pD 4.0
100% D2O
5
4.0
ambient
303
NMR Spectrometer Information
Spectrometer
Manufacturer
Model
Field Strength
1
Varian
INOVA
500
NMR Refinement
Method
Details
Software
torsion angle dynamics
Structures are based on a total of 705 constraints, 679 are meaningful nOe derived constraints (642 unambiguous, 37 ambiguous), 16 are dihedral (phi) angle constraints and 10 are hydrogen bonds. The four disulfide bridges (CYS 6-27, 12-32, 16-34, 22-37) were included in the topology file used for the calculations.
VNMR
NMR Ensemble Information
Conformer Selection Criteria
structures with the lowest energy
Conformers Calculated Total Number
20
Conformers Submitted Total Number
10
Representative Model
1 (lowest energy)
Additional NMR Experimental Information
Details
Disulfide bridges were determined by NMR and by N-terminal sequencing of proteolysis peptides.
Distance constraints were derived from initial nOe build up rates using 2D NOESY experiments with mixing times of 70, 100, 150, 200 and 250 ms in H2O and D2O.