YscN

yscN is a gene name used in Yersinia species to denote the ATPase component of their type III secretion system (T3SS), also known as the secretion injectisome. The gene is part of the ysc gene cluster that encodes structural and regulatory components of the T3SS, often located on the virulence plasmid pYV, though some species may carry related loci on the chromosome.

Protein product and role: YscN is a cytosolic AAA+ ATPase that energizes secretion by hydrolyzing ATP. It typically forms oligomeric complexes and interacts with other cytosolic and membrane components of the T3SS; through ATP hydrolysis, it drives the unfolding and translocation of effector proteins through the secretion apparatus. The activity of YscN is essential for the secretion of Yersinia effector proteins (Yops) and for the proper assembly of the injectisome. Loss of YscN function markedly reduces or abolishes secretion and virulence in many Yersinia models.

Regulation and expression: Expression of yscN is co-regulated with other T3SS genes and is influenced by environmental cues such as temperature and calcium, as part of the T3SS regulation network controlled by transcriptional regulators like LcrF. The gene is usually co-transcribed with neighboring yop/ysc cluster genes.

Homology and broader context: YscN is homologous to other type III secretion system ATPases, such as InvC in Salmonella and PscN in Pseudomonas, and is commonly referred to as SctN in broader T3SS nomenclature. Comparative studies help illuminate the evolution and mechanism of bacterial secretion systems.