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J. Bacteriol., 12 1995, 7019-7025, Vol 177, No. 24
A Kuroda, T Kumano, K Taguchi, T Nikata, J Kato and H Ohtake
A Pseudomonas aeruginosa mutant, defective in taxis toward L-serine but
responsive to peptone, was selected by the swarm plate method after N-
methyl-N'-nitrosoguanidine mutagenesis. The mutant, designated PCT1, was
fully motile but failed to show chemotactic responses to glycine, L-
serine, L-threonine, and L-valine. PCT1 also showed weaker responses to
some other commonly occurring L-amino acids than did the wild-type strain
PAO1. A chemotactic transducer gene, denoted pctA (Pseudomonas chemotactic
transducer A), was cloned by phenotypic complementation of PCT1. Nucleotide
sequence analysis showed that the pctA gene encodes a putative polypeptide
of 629 amino acids with a calculated mass of 68,042. A hydropathy plot of
the predicted polypeptide suggested that PctA may be an integral membrane
protein with two potential membrane- spanning regions. The C-terminal
domain of PctA showed high homology with the enteric methyl-accepting
chemotaxis proteins (MCPs). The most significant amino acid sequence
similarity was found in the region of MCPs referred to as the highly
conserved domain. The pctA gene was inactivated by insertion of a kanamycin
resistance gene cassette into the wild-type gene, resulting in the same
observed deficiency in taxis toward L-amino acids as PCT1. In vivo methyl
labeling experiments with L-[methyl-3H]methionine showed that this knockout
mutant lacked an MCP with a molecular weight of approximately 68,000.
Copyright © 1995, American Society for Microbiology
Molecular cloning and characterization of a chemotactic transducer gene in Pseudomonas aeruginosa
Department of Fermentation Technology, Hiroshima University, Japan.
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