PscN

PscN is the ATPase component of the type III secretion system (T3SS) in Pseudomonas aeruginosa and related Gram-negative bacteria. It is encoded by the pscN gene within the T3SS gene cluster and is homologous to SctN proteins found in other pathogens. PscN is a cytoplasmic enzyme that provides the energy required to assemble and secrete effector proteins through the T3SS injectisome.

Functionally, PscN forms a hexameric ring belonging to the AAA+ family. It hydrolyzes ATP to drive the unfolding and translocation of substrates through the secretion apparatus, enabling the export of both early and later substrates. It also participates in engaging chaperone–substrate complexes and interfaces with regulatory elements that govern substrate specificity and secretion timing.

Structurally, PscN operates in the cytoplasm as part of the bacterial secretion core. Its activity is coordinated with other T3SS components and regulatory factors that determine when and which substrates are secreted. The precise protein-protein interactions within the sorting platform help ensure efficient energy use and correct delivery of virulence proteins.

Role in virulence and regulation: PscN is essential for functional T3SS activity and virulence in P. aeruginosa; loss or impairment of its ATPase activity disrupts secretion and attenuates pathogenicity. Expression of pscN is part of the T3SS regulon and is regulated by environmental signals and transcriptional regulators such as ExsA.

Clinical and research relevance: Because the T3SS is a major virulence determinant, PscN is studied as a potential target for anti-virulence strategies aimed at disarming bacteria rather than inhibiting growth.