FimV is a
Pseudomonas aeruginosainner membrane protein that regulates intracellular cyclic AMP (cAMP) levels—and thus type IV pilus (T4P)-mediated twitching motility and type II secretion (T2S)—by activating the adenylate cyclase CyaB. Its cytoplasmic domain contains three predicted tetratricopeptide repeat (TPR) motifs separated by an unstructured region: two proximal to the inner membrane and one within the “FimV C-terminal domain,” which is highly conserved across diverse homologs. Here, we present the crystal structure of the FimV C terminus, FimV861–919, containing a TPR motif decorated with solvent-exposed, charged side chains, plus a C-terminal capping helix. FimV689, a truncated form lacking this C-terminal motif, did not restore wild-type levels of twitching or surface piliation compared to the full-length protein. FimV689failed to restore wild-type levels of the T4P motor ATPase PilU or T2S, suggesting that it was unable to activate cAMP synthesis. Bacterial two-hybrid analysis showed that TPR3 interacts directly with the CyaB activator, FimL. However, FimV689failed to restore wild-type motility in a fimVmutant expressing a constitutively active CyaB ( fimV cyaB-R456L), suggesting that the C-terminal motif is also involved in cAMP-independent functions of FimV. The data show that the highly conserved TPR-containing C-terminal domain of FimV is critical for its cAMP-dependent and -independent functions. IMPORTANCEFimV is important for twitching motility and cAMP-dependent virulence gene expression in P. aeruginosa. FimV homologs have been identified in several human pathogens, and their functions are not limited to T4P expression. The C terminus of FimV is remarkably conserved among otherwise very diverse family members, but its role is unknown. We provide here biological evidence for the importance of the C-terminal domain in both cAMP-dependent (through FimL) and -independent functions of FimV. We present X-ray crystal structures of the conserved C-terminal domain and identify a consensus sequence for the C-terminal TPR within the conserved domain. Our data extend our knowledge of FimV's functionally important domains, and the structures and consensus sequences provide a foundation for studies of FimV and its homologs.