Figure 2. Structure of the M1-C N-terminal domain.

(a) Ribbon diagram of M1-C composed of two four-helical bundles connected by helix 5. Alpha helices are labeled. (b) Close up of the Mg²⁺ binding sites. M1-C binds two Mg²⁺ ions coordinated by residues from helices 5 and 8 and six water molecules. Alpha helices are labeled. (c) Superposing of the Cα atoms of M1-A and M1-C reveals an overall similar fold and the displacement of helix 6.