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Infection and Immunity, August 2004, p. 4619-4627, Vol. 72, No. 8
0019-9567/04/$08.00+0     DOI: 10.1128/IAI.72.8.4619-4627.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Multiple Functions of the Leucine-Rich Repeat Protein LrrA of Treponema denticola

Akihiko Ikegami,1 Kiyonobu Honma,2 Ashu Sharma,1 and Howard K. Kuramitsu1*

Department of Oral Biology, School of Dental Medicine, State University of New York, Buffalo, New York 14214,1 Department of Microbiology, Oral Health Science Center, Tokyo Dental College, Chiba 261-8502, Japan2

Received 27 October 2003/ Returned for modification 31 December 2003/ Accepted 26 April 2004

The gene lrrA, encoding a leucine-rich repeat protein, LrrA, that contains eight consensus tandem repeats of 23 amino acid residues, has been identified in Treponema denticola ATCC 35405. A leucine-rich repeat is a generally useful protein-binding motif, and proteins containing this repeat are typically involved in protein-protein interactions. Southern blot analysis demonstrated that T. denticola ATCC 35405 expresses the lrrA gene, but the gene was not identified in T. denticola ATCC 33520. In order to analyze the functions of LrrA in T. denticola, an lrrA-inactivated mutant of strain ATCC 35405 and an lrrA gene expression transformant of strain ATCC 33520 were constructed. Characterization of the mutant and transformant demonstrated that LrrA is associated with the extracytoplasmic fraction of T. denticola and expresses multifunctional properties. It was demonstrated that the attachment of strain ATCC 35405 to HEp-2 cell cultures and coaggregation with Tannerella forsythensis were attenuated by the lrrA mutation. In addition, an in vitro binding assay demonstrated specific binding of LrrA to a portion of the Tannerella forsythensis leucine-rich repeat protein, BspA, which is mediated by the N-terminal region of LrrA. It was also observed that the lrrA mutation caused a reduction of swarming in T. denticola ATCC 35405 and consequently attenuated tissue penetration. These results suggest that the leucine-rich repeat protein LrrA plays a role in the attachment and penetration of human epithelial cells and coaggregation with Tannerella forsythensis. These properties may play important roles in the virulence of T. denticola.


* Corresponding author. Mailing address: Department of Oral Biology, State University of New York, Buffalo, NY 14214. Phone: (716) 829-2068. Fax: (716) 829-3942. E-mail: Kuramits{at}buffalo.edu.

Editor: V. J. DiRita


Infection and Immunity, August 2004, p. 4619-4627, Vol. 72, No. 8
0019-9567/04/$08.00+0     DOI: 10.1128/IAI.72.8.4619-4627.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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