title: The product of tadZ, a new member of the parA/minD superfamily, localizes to a pole in Aggregatibacter actinomycetemcomitans.
abstract: Aggregatibacter actinomycetemcomitans establishes a tenacious biofilm that is important for periodontal disease. The tad locus encodes the components for the secretion and biogenesis of Flp pili, which are necessary for the biofilm to form. TadZ is required, but its function has been elusive. We show that tadZ genes belong to the parA/minD superfamily of genes and that TadZ from A. actinomycetemcomitans (AaTadZ) forms a polar focus in the cell independent of any other tad locus protein. Mutations indicate that regions in AaTadZ are required for polar localization and biofilm formation. We show that AaTadZ dimerizes and that all TadZ proteins are predicted to have a Walker-like A box. However, they all lack the conserved lysine at position 6 (K6) present in the canonical Walker-like A box. When the alanine residue (A6) in the atypical Walker-like A box of AaTadZ was converted to lysine, the mutant protein remained able to dimerize and localize, but it was unable to allow the formation of a biofilm. Another essential biofilm protein, the ATPase (AaTadA), also localizes to a pole. However, its correct localization depends on the presence of AaTadZ. We suggest that the TadZ proteins mediate polar localization of the Tad secretion apparatus.
authors.affiliation: Department of Microbiology & Immunology, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA.
authors.forename: Brenda A
authors.initials: BA
authors.lastname: Perez-Cheeks
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Planet
authors.forename: I Neil
authors.initials: IN
authors.lastname: Sarkar
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Clock
authors.forename: Qingping
authors.initials: Q
authors.lastname: Xu
authors.forename: David H
authors.initials: DH
authors.lastname: Figurski
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000032:analysis* / Q000235:genetics; D018441:Biofilms / Q000254:growth & development; D004252:DNA Mutational Analysis; D008856:Microscopy, Fluorescence; D015661:Pasteurellaceae / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D010802:Phylogeny; D055503:Protein Multimerization; D021381:Protein Transport; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins