1N8M

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.

Computation: NMR Software
#	Classification	Version	Software Name	Author
1	collection	VNMR	6.1C	Varian Inc.
2	data analysis	NMRView	5.03	Johnson
3	structure solution	ARIA	1.2	Nilges
4	structure solution	CNS	1.1	Brunger
5	refinement	CNS	1.1	Brunger

RCSB PDB Core Operations are funded by the U.S. National Science Foundation (DBI-2321666), the US Department of Energy (DE-SC0019749), and the National Cancer Institute, National Institute of Allergy and Infectious Diseases, and National Institute of General Medical Sciences of the National Institutes of Health under grant R01GM133198.