Figure 1: The Rcs phosphorelay system.

A) Domain architecture of Klebsiella pneumoniae Rcs proteins; not drawn to scale. E. coli Rcs proteins are similar in organization and only slightly differ in size and domain borders (see Fig. S1A). Important residues for the phosphorelay are indicated by red dots. RcsC and RcsD have similar domain architectures, but RcsD contains a Hpt phosphotransfer domain along with an inactive histidine kinase domain. RcsB contains the aspartate residue which is phosphorylated during signaling. RcsF is lipidated, contains a disordered linker and a C-terminal region that interacts with IgaA. The periplasmic domain of IgaA interacts with RcsD/RcsF while the cytoplasmic domains interact only with RcsD. B) Snapshot of the Rcs phosphorelay signaling cascade at start of this project.