PilT and PilU are homohexameric ATPases that coordinate to retract type IVa pili

Autoři: Jennifer L. Chlebek aff001;  Hannah Q. Hughes aff001;  Aleksandra S. Ratkiewicz aff002;  Rasman Rayyan aff002;  Joseph Che-Yen Wang aff003;  Brittany E. Herrin aff001;  Triana N. Dalia aff001;  Nicolas Biais aff002;  Ankur B. Dalia aff001
Působiště autorů: Department of Biology, Indiana University, Bloomington, Indiana, United States of America aff001;  Biology Department and Graduate Center, City University of New York, Brooklyn, New York, United States of America aff002;  Electron Microscopy Center, Indiana University, Bloomington, Indiana, United States of America aff003
Vyšlo v časopise: PilT and PilU are homohexameric ATPases that coordinate to retract type IVa pili. PLoS Genet 15(10): e32767. doi:10.1371/journal.pgen.1008448
Kategorie: Research Article
doi: 10.1371/journal.pgen.1008448


Bacterial type IV pili are critical for diverse biological processes including horizontal gene transfer, surface sensing, biofilm formation, adherence, motility, and virulence. These dynamic appendages extend and retract from the cell surface. In many type IVa pilus systems, extension occurs through the action of an extension ATPase, often called PilB, while optimal retraction requires the action of a retraction ATPase, PilT. Many type IVa systems also encode a homolog of PilT called PilU. However, the function of this protein has remained unclear because pilU mutants exhibit inconsistent phenotypes among type IV pilus systems and because it is relatively understudied compared to PilT. Here, we study the type IVa competence pilus of Vibrio cholerae as a model system to define the role of PilU. We show that the ATPase activity of PilU is critical for pilus retraction in PilT Walker A and/or Walker B mutants. PilU does not, however, contribute to pilus retraction in ΔpilT strains. Thus, these data suggest that PilU is a bona fide retraction ATPase that supports pilus retraction in a PilT-dependent manner. We also found that a ΔpilU mutant exhibited a reduction in the force of retraction suggesting that PilU is important for generating maximal retraction forces. Additional in vitro and in vivo data show that PilT and PilU act as independent homo-hexamers that may form a complex to facilitate pilus retraction. Finally, we demonstrate that the role of PilU as a PilT-dependent retraction ATPase is conserved in Acinetobacter baylyi, suggesting that the role of PilU described here may be broadly applicable to other type IVa pilus systems.

Klíčová slova:

Adenosine triphosphatase – Fluorescence imaging – Glycerol – Hyperexpression techniques – Mutant strains – Phenotypes – Pili and fimbriae – Vibrio cholerae


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