TCPP

TcpP is a regulatory protein found in Vibrio cholerae that plays a key role in controlling virulence gene expression. It is part of the ToxR regulon, a network of transcriptional regulators that coordinate the expression of factors involved in pathogenicity. TcpP functions in conjunction with TcpH and interacts with ToxR to influence the transcriptional cascade that leads to virulence factor production.

In the virulence regulatory pathway of V. cholerae, environmental signals encountered in the host trigger a regulatory hierarchy. TcpP, together with TcpH, supports ToxR activity and promotes the activation of toxT, the transcription factor that directly activates downstream virulence genes. The toxT-driven program induces expression of the toxin-coregulated pilus (tcpA) and cholera toxin (ctxAB), among other virulence determinants, enabling colonization and disease.

Structurally, TcpP is a membrane-associated protein with domains that span or associate with the inner membrane and periplasm, enabling interactions with TcpH and ToxR in the cell envelope. These interactions help stabilize regulatory complexes and modulate transcriptional responses to environmental cues such as pH, bile, and temperature. TcpP is typically described as a positive regulator whose activity is contingent on its association with TcpH and its integration into the broader ToxR regulon.

Mutants lacking tcpP often show reduced expression of tcpA and ctxAB and attenuated virulence in model systems, underscoring its role in enabling full virulence gene expression in response to host signals.

See also: ToxR, ToxS, ToxT, TcpH, TcpA, ctxAB.