Crystal structures of the pilus retraction motor PilT suggest large domain movements and subunit cooperation drive motility.
PilT is a hexameric ATPase required for bacterial type IV pilus retraction and surface motility. Crystal structures of ADP- and ATP-bound Aquifex aeolicus PilT at 2.8 and 3.2 A resolution show N-terminal PAS-like and C-terminal RecA-like ATPase domains followed by a set of short C-terminal helices. The hexamer is formed by extensive polar subunit interactions between the ATPase core of one monomer and the N-terminal domain of the next. An additional structure captures a nonsymmetric PilT hexamer in which approach of invariant arginines from two subunits to the bound nucleotide forms an enzymatically competent active site. A panel of pilT mutations highlights the importance of the arginines, the PAS-like domain, the polar subunit interface, and the C-terminal helices for retraction. We present a model for ATP binding leading to dramatic PilT domain motions, engagement of the arginine wire, and subunit communication in this hexameric motor. Our conclusions apply to the entire type II/IV secretion ATPase family.
Satyshur
Kenneth A
KA
Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA.
Worzalla
Gregory A
GA
Meyer
Lorraine S
LS
Heiniger
Erin K
EK
Aukema
Kelly G
KG
Misic
Ana M
AM
Forest
Katrina T
KT
D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D000595:Amino Acid Sequence; D001120:Arginine / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D018360:Crystallography, X-Ray; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology*; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009068:Movement / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000235:genetics; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*
D001426:Bacterial Proteins; D020409:Molecular Motor Proteins; D021122:Protein Subunits; D001120:Arginine; D000251:Adenosine Triphosphatases