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. 2020 Oct 13;3:568. doi: 10.1038/s42003-020-01283-8

Fig. 6. Role of calcium in TgELCs.

Fig. 6

a Crystal structure of the glideosome trimeric complex composed of TgELC1 (green), MLC1 (orange) and TgMyoA-C (pink) in the absence of calcium (complex 1 f). The absence of calcium does not cause a major structural rearrangement (see Fig. 5a). b Structural comparison of the first EF hand in ELCs and calcium coordination between complex 1f, complex 1, complex 2 and PfELC-N. Whereas PfELC does not bind any ion due to a degenerated sequence in its EF hand, both TgELCs in complex 1 and complex 2 bind calcium in a tetragonal bipyramid coordination, including two water molecules. These water molecules are further stabilized in complex 2 by additional residues (E27, Q49, D20). In complex 1f, the side chain of residue D17 is flipped by 120°, enabling the release of calcium. c, d Thermal stability change of trimeric complex 1 and complex 2 upon addition of calcium measured by nanoDSF. The stability of both complexes strongly increases upon calcium binding.