Estimating affinities of calcium ions to proteins

Ca(2+)-ions have a range of affinities to different proteins, depending on the various functions of these proteins. This makes the determination of Ca(2+)-protein affinities an interesting subject for functional studies. We have investigated the performance of two methods - Fold-X and AutoDock vina - in the prediction of Ca(2+)-protein affinities. Both methods, although based on different energy functions, showed virtually the same correlation with experimental affinities. Guided by insight from experiment, we further derived a simple linear model based on the solvent accessible surface of Ca(2+) that had practically the same performance in terms of absolute errors as the more complex docking methods.