PilTNTPase

PilTNTPase, commonly referred to as PilT NTPase, is an ATPase that powers retraction of type IV pili in many bacteria. It is a cytoplasmic hexameric enzyme that couples ATP hydrolysis to pilus disassembly at the base, producing retraction and enabling surface-associated twitching motility. PilTNTPase often functions in opposition to extension motors such as PilB, coordinating cycles of pilus extension and retraction essential for surface exploration and adherence.

Biochemically, PilTNTPase belongs to the AAA+ family of P-loop NTPases. It binds and hydrolyzes ATP via conserved Walker A and Walker B motifs, driving conformational changes that transduce energy to the pilus fiber. The active enzyme typically forms a hexameric ring; conformational changes in subunits pull the pilus filament inward. PilTNTPase interacts with core assembly proteins in the inner membrane, including PilC and other platform components, to control the assembly-disassembly cycle. It often works in concert with PilB, the extension motor, to regulate pilus length and dynamics.

Genetic and distribution: pilT is widely conserved among Gram-negative bacteria possessing type IV pili and is frequently found within pil or tad operons. Some organisms harbor multiple PilT-like NTPases with distinct roles in pilus dynamics or competence, reflecting adaptation to different environmental niches or infection contexts.

Significance: PilTNTPase-mediated retraction is a key determinant of twitching motility, surface adhesion, microcolony formation, and, in some species, natural competence and virulence. Because of its central role in pilus dynamics, PilTNTPase is a potential target for interventions aimed at reducing bacterial adhesion and spread.