title: A force-dependent switch reverses type IV pilus retraction.
abstract: Type IV pilus dynamics is important for virulence, motility, and DNA transfer in a wide variety of prokaryotes. The type IV pilus system constitutes a very robust and powerful molecular machine that transports pilus polymers as well as DNA through the bacterial cell envelope. In Neisseria gonorrhoeae, pilus retraction is a highly irreversible process that depends on PilT, an AAA ATPase family member. However, when levels of PilT are reduced, the application of high external forces (F = 110 +/- 10 pN) induces processive pilus elongation. At forces of >50 pN, single pili elongate at a rate of v = 350 +/- 50 nm/s. For forces of <50 pN, elongation velocity depends strongly on force and relaxation causes immediate retraction. Both pilus retraction and force-induced elongation can be modeled by chemical kinetics with same step length for the rate-limiting translocation step. The model implies that a force-dependent molecular switch can induce pilus elongation by reversing the retraction mechanism.
authors.affiliation: Department of Biological Sciences, Columbia University, 1212 Amsterdam Avenue, New York, NY 10027.
authors.forename: Berenike
authors.initials: B
authors.lastname: Maier
authors.forename: Michael
authors.initials: M
authors.lastname: Koomey
authors.forename: Michael P
authors.initials: MP
authors.lastname: Sheetz
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000502:physiology* / Q000648:ultrastructure; D007700:Kinetics; D020409:Molecular Motor Proteins / Q000235:genetics; D009344:Neisseria gonorrhoeae / Q000235:genetics* / Q000472:pathogenicity*; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D020409:Molecular Motor Proteins; D000251:Adenosine Triphosphatases