title: Functional dissection of a conserved motif within the pilus retraction protein PilT.
abstract: PilT is a hexameric ATPase required for type IV pilus retraction in gram-negative bacteria. Retraction of type IV pili mediates intimate attachment to and signaling in host cells, surface motility, biofilm formation, natural transformation, and phage sensitivity. We investigated the in vivo and in vitro roles of each amino acid of the distinct, highly conserved C-terminal AIRNLIRE motif in PilT. Substitution of amino acids A288, I289, L292, and I293 as well as a double substitution of R290 and R294 abolished Pseudomonas aeruginosa PilT function in vivo, as measured by a loss of surface motility and phage sensitivity. When introduced into purified Aquifex aeolicus PilT, substitutions in the AIRNLIRE motif did not disrupt ATPase activity or oligomerization. In contrast, a K136Q substitution in the broadly conserved nucleotide binding motif prevented PilT function in vivo as well as in vitro. We propose that the AIRNLIRE motif forms an amphipathic alpha helix which transmits signals between a surface-exposed protein interaction site and the ATPase core of PilT, and we recognize a potential functional homology in other type II secretion ATPases.
authors.affiliation: Department of Bacteriology, 420 Henry Mall, University of Wisconsin-Madison, Madison, WI 53706-1521, USA.
authors.forename: Kelly G
authors.initials: KG
authors.lastname: Aukema
authors.forename: Erin M
authors.initials: EM
authors.lastname: Kron
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Herdendorf
authors.forename: Katrina T
authors.initials: KT
authors.lastname: Forest
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D017124:Conserved Sequence; D004252:DNA Mutational Analysis; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D009068:Movement; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D017433:Protein Structure, Secondary; D017105:Pseudomonas Phages / Q000254:growth & development; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000502:physiology*; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D020409:Molecular Motor Proteins; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases