Figure 1: Organization of MapZ and NMR characterization of its extracellular domain.

(a) Architecture of MapZ. MapZ is composed of a cytoplasmic (in yellow) and an extracellular domain (in blue; residues 1–158 and 182–464, respectively), connected through a transmembrane α-helix (in grey). The extracellular domain of MapZ (MapZ_extra) is predicted by bioinformatic approaches¹⁵ to be divided in two independent subdomains MapZ_extra1 (in dark blue) and MapZ_extra2 (in pale blue) linked by a flexible serine-rich stretch (from residues 314–354). MapZ_extra1 and MapZ_extra2 extend from residues 182–313 and 355–464, respectively. (b) 2D-[¹H,¹⁵N]-BEST-TROSY of MapZ_extra1 (left), MapZ_extra2 (middle) and MapZ_extra (right). Assignment of the resonances of the MapZ_extra1 and MapZ_extra2 subdomains is displayed in turquoise and magenta, respectively. A full resonance assignment of the MapZ_extra spectrum is reported in Supplementary Fig. 3. (c) Excerpts of the superimposition of the 2D-[¹H,¹⁵N]-BEST-TROSY spectra of MapZ_extra1 (turquoise), MapZ_extra2 (magenta) and MapZ_extra (black). Assignments for the full-length construct are reported in black for each of the resonances. They all show a good overlay with resonances of the individual subdomains, with the exception of K308 that is affected due to its location at the C terminus of MapZ_extra1 (in the later construct the resonance is superimposed with the resonance in magenta of N393) and of Q316, which is part of the SRL and thus absent from MapZ_extra1 or MapZ_extra2. This superimposition highlights the preservation of the fold of the isolated subdomains in the full-length construct, as outlined by dashed lines in b.