Structural differences among subfamilies of EF‐hand proteins—A view from the pseudo two‐fold symmetry axis

We have analyzed the conformations of EF‐lobes, adjacent pairs of EF‐hand domains, in a coordinate system based on the approximate two‐fold (z) axis that relates the two EF‐hands. Two parameters ‐ dE(ø), the azimuthal angle between the y‐axis and the projection of the offset vector to helix E onto the yz‐plane, and δdF(ø), the difference angle between the two helices (F1 and F2) of odd and even domains—characterize the openness of a single EF‐hand domain and of an EF‐lobe, respectively. We describe and compare values of dE(ø) and of δdF(ø) for EF‐hand proteins of five subfamilies—CTER, CPV, S100, PARV, CALP—in calci‐ and apo‐ forms, with and without bound target proteins. Each subfamily has characteristic changes associated with binding calcium and/or target proteins. Proteins 2014; 82:2915–2924. © 2014 Wiley Periodicals, Inc.