SctN

sctN is a gene encoding a cytosolic ATPase that powers the Type III secretion system (T3SS) in many Gram-negative bacteria. In different species orthologs are named yscN (Yersinia), invC (Salmonella), or spa47 (Shigella).

The SctN family belongs to the AAA+ ATPases and typically forms a hexameric ring that hydrolyzes ATP to energize secretion. It resides in the cytoplasmic portion of the injectisome and couples ATP hydrolysis to unfolding and translocation of effector proteins through the T3SS needle.

Structurally, SctN contains an ATPase domain with Walker A and Walker B motifs and interacts with cytoplasmic components such as SctL, SctQ, and SctV to form a functional ATPase complex. These interactions help coordinate substrate recognition, substrate unfolding, and energy supply for passage through the secretion channel.

SctN is broadly distributed among pathogenic Gram-negative bacteria and is absent or divergent in many non-pathogenic strains. Because of its essential role in virulence, SctN is a focus of antivirulence strategies; mutations or inhibitors that reduce ATPase activity impair secretion and host cell invasion.

In research, structural and biochemical studies of SctN and its homologs have informed models of hexameric assembly, substrate engagement, and the coupling of energy to secretion. These insights support understanding of T3SS function and the development of therapeutic approaches targeting bacterial virulence.

See also: Type III secretion system; YscN; InvC; Spa47.