Table 1.

NMR-derived restraints and statistics of 20 NMR structures¹

	<20>	best
rmsd from distance constraints (Å)2
total (3382)	0.037 ± 0.002	0.036
intraresidue (570)	0.009 ± 0.004	0.010
sequential ( |i − j| = 1) (962)	0.029 ± 0.003	0.028
medium range (1 < |i − j| ≤1) (848)	0.036 ± 0.003	0.035
long range ( |i − j| > 5) (446)	0.045 ± 0.005	0.045
intermolecular for dimer interface (130)	0.044 ± 0.006	0.034
ambiguous intra- or inter- S100A1 subunit (38)	0.012 ± 0.010	0.005
TRTK12 peptide (seq, med) (90)	0.028 ± 0.009	0.041
Intermolecular S100A1 to TRTK12 peptide (96)	0.060 ± 0.011	0.062
calcium ligand (18)	0.025 ± 0.010	0.029
hydrogen bonds (184)	0.069 ± 0.005	0.064
rmsd from exptl dihedral constraints (°)
Φ,Ψ (276)	0.516 ± 0.120	0.502
rmsd from dipolar coupling restraints (Hz)
DNH (112)	1.652 ± 0.093	1.606
DCH (136)	3.296 ± 0.171	3.261
rmsd from exptl13C chemical shifts
13Cα (ppm)	1.261 ± 0.041	1.253
13Cβ (ppm)	1.054 ± 0.039	1.020
rmsd from idealized geometry
bonds (Å)	0.006 ± 0.001	0.006
angles (°)	0.978 ± 0.018	0.959
impropers (°)	1.841 ± 0.010	1.844
Lennard-Jones potential energy (kcal/mol)3	−889 ± 28	−917
Q-factor4	0.26 ±0.04	0.25
% of residues in the most favorable region of the Ramachandran plot5	87.6 ± 2.4	91.3
Rmsd to the mean structure (Å)6
all backbone atoms in S100A1 (3–88)	0.518 ± 0.088	0.339
all heavy atoms in S100A1 (3–88)	1.097 ± 0.128	0.943
all ordered backbone (S100A1 3–88, TRTK12 4–12)	0.565 ± 0.089	0.476
all heavy atoms (S100A1 3–88, TRTK12 4–12)	1.118 ± 0.118	0.969

¹The 20 ensemble structures, <20>, are the results of simulated annealing calculations. The best structure is the closest to the average structure. The values shown for the <20> are the mean ± standard deviation.

²All four subunits of the protein complex are included in all of these values. None of the 20 structures has a distance violation > 0.4 Å or a dihedral angle violation of > 5°. The force constants used in the SA calculations are as follows: 1000 kcal mol ⁻¹ Ų for bond length, 500 kcal mol⁻¹ rad⁻² for angles and improper torsions, 4 kcal mol⁻¹ Å⁻⁴ for the quartic van der Waals (vdw) repulsion term (hard-sphere effective vdw set to 0.8 times their values in CHARMm parameters), 50 kcal mole⁻¹ Å⁻² for experimental distance constraints, 100 kcal mol⁻¹ Å⁻² for non-crystallographic symmetry, 1kcal mol⁻¹ Å⁻² for distance symmetry constraints, 0.5 kcal mol⁻¹ ppm⁻² for the ¹³C chemical shift constraints, and 1.0 for the conformational database potential. The force constants (in kcal Hz⁻²) used for dipolar coupling restraints were as follows: 0.40 for ¹⁵N-¹H^N and 0.2 for ¹³C^α-¹H^α.

³Lennard-Jones van der Waals energies were calculated using CHARMm parameters and were not used in any stage of the structure determination

⁴Q-values were determined by randomly removing 10% of all RDC values. To ensure accuracy, an ensemble of structures with a second randomly removed subset of RDCs was also run. The Q-value of this second set was 0.26.

⁵PROCHECK was utilized to generate the Ramachandran plot.

⁶Backbone calculations include C^α, N, and C′ atoms. Only residues 3–88 are included since no long-range NOE correlations were observed for residues 1–2 and 89–93 in S100A1 or residues 1–3 in the TRTK peptide.