TABLE 2.
The coordination numbers of protein-bound Na+ (Na+ c.n.) and Ca2+ (Ca2+ c.n.) ions at the 10 cation binding sites (Fig. 4 b), determined as the number of oxygen atoms within the first coordination shell (2.5 Å) of the ion, averaged over the frames in which a protein-bound ion existed
| Cation-Ligand | D238:D350 | E239:D346 | E220:D408 | E80:E417 | E339:E343 | D132:E133 | D127:E236 | E299:D332 | D290:E363 | E451:D454 |
|---|---|---|---|---|---|---|---|---|---|---|
| Na+ c.n. | 4.7 | 4.7 | 4.7 | 4.6 | 4.6 | 4.6 | 3.3 | 4.4 | 4.6 | 4.5 |
| Na+-O:water | 3.0 | 2.6 | 2.3 | 2.0 | 2.8 | 3.2 | 2.3 | 3.0 | 2.7 | 3.0 |
| Na+-O:protein backbone | 0.0 | 0.0 | 0.2 | 0.4 | 0.0 | 0.2 | 0.3 | 0.0 | 0.3 | 0.0 |
| Na+-O:protein side chain | 1.7 | 2.1 | 2.2 | 2.2 | 1.8 | 1.2 | 0.7 | 1.4 | 1.6 | 1.5 |
| Ca2+ c.n. | 6.6 | 6.9 | 6.3 | 7.0 | 6.6 | 7.2 | 7.0 | 7.0 | 6.8 | 7.0 |
| Ca2+-O:water | 4.0 | 4.9 | 4.2 | 5.0 | 4.0 | 3.9 | 3.9 | 3.8 | 4.8 | 5.0 |
| Ca2+-O:protein backbone | 0.0 | 0.0 | 0.3 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Ca2+-O:protein side chain | 2.6 | 2.0 | 1.8 | 2.0 | 2.6 | 3.3 | 3.1 | 3.2 | 2.0 | 2.0 |
The data reported is for system 2 for Na+ and system 5 for Ca2+. Na+(/Ca2+)-O:water refers to the average number of liganding oxygen atoms from water; Na+(/Ca2+)-O:protein backbone and Na+(/Ca2+)-O:protein side chain refer to the average number of oxygen atoms from the protein backbone and side chain, respectively.