Figure 5.

Mutation of the longitudinal interface leads to assembly deficiency. (A) Light scattering was used to monitor polymerization of MamK^WT and MamK^Mut, at various protein concentrations. For each sample, the light scattering intensity (in arbitrary units) is plotted over time. MamK^Mut has a higher critical assembly concentration, due to its reduced nucleation capacity. (B) Negative‐stain electron micrographs of MamK^WT and MamK^Mut, at various protein concentration, confirming that the light scattering signal in (A) corresponds to filament assembly. (C) GFP‐tagged MamK^WT or MamK^Mut was expressed in AMB‐1 (left) or a mutant strain lacking the mamK gene (right), and the resulting bacteria were observed by fluorescence microscopy. A green fluorescent filament is observed when MamK^WT is expressed, regardless of the strain. When MamK^Mut is expressed, it is incorporated in the MamK filament in the WT strain, but cannot assemble on its own in the ΔmamK strain. The quantification of the corresponding images is shown in the right panel.