PscK

PscK is a component of the type III secretion system (T3SS) in Pseudomonas species, most notably Pseudomonas syringae. It is encoded within the T3SS gene cluster and is conserved among bacteria that rely on a T3SS for pathogenic interactions or symbiosis. As a small cytoplasmic-associated protein, PscK is linked to the basal-body region of the secretion apparatus.

PscK localizes to the cytoplasmic side of the T3SS basal body and is thought to contribute to the assembly and stability of the secretion machinery. It is considered part of the network that connects core basal-body components to the cytoplasmic framework, helping to organize the interface between membrane-embedded elements and cytosolic factors involved in secretion.

Biochemical and structural studies support an interaction between PscK and other basal-body proteins, particularly PscD. The PscK–PscD interface is implicated in proper assembly and function of the T3SS, and genetic disruption of pscK often leads to defects in secretion or needle complex formation, indicating an essential role for PscK in translocation.

Structural analyses have provided insights into the fold of PscK and its complex with PscD, informing models of T3SS basal-body organization. PscK is the Pseudomonas ortholog of SctK/YscK found in other Gram-negative bacteria, reflecting a conserved role across diverse organisms that possess type III secretion systems.

In summary, PscK is a conserved T3SS component that participates in basal-body assembly and function by interfacing with other core components, contributing to the proper operation of the secretion system in Pseudomonas species.