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Infection and Immunity, January 2007, p. 91-103, Vol. 75, No. 1
0019-9567/07/$08.00+0     doi:10.1128/IAI.00120-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Identification of the Actinobacillus pleuropneumoniae Leucine-Responsive Regulatory Protein and Its Involvement in the Regulation of In Vivo-Induced Genes{triangledown}

Trevor K. Wagner and Martha H. Mulks*

Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan 48824

Received 23 January 2006/ Returned for modification 19 April 2006/ Accepted 12 October 2006

Actinobacillus pleuropneumoniae is a gram-negative bacterial pathogen that causes a severe hemorrhagic pneumonia in swine. We have previously shown that the limitation of branched-chain amino acids (BCAAs) is a cue that induces the expression of a subset of A. pleuropneumoniae genes identified as specifically induced during infection of the natural host animal by using an in vivo expression technology screen. Leucine-responsive regulatory protein (Lrp) is a global regulator and has been shown in Escherichia coli to regulate many genes, including genes involved in BCAA biosynthesis. We hypothesized that A. pleuropneumoniae contains a regulator similar to Lrp and that this protein is involved in the regulation of a subset of genes important during infection and recently shown to have increased expression in the absence of BCAAs. We report the identification of an A. pleuropneumoniae serotype 1 gene encoding a protein with similarity to amino acid sequence and functional domains of other reported Lrp proteins. We further show that purified A. pleuropneumoniae His6-Lrp binds in vitro to the A. pleuropneumoniae promoter regions for ilvI, antisense cps1AB, lrp, and nqr. A genetically defined A. pleuropneumoniae lrp mutant was constructed using an allelic replacement and sucrose counterselection method. Analysis of expression from the ilvI and antisense cps1AB promoters in wild-type, lrp mutant, and complemented lrp mutant strains indicated that Lrp is required for induction of expression of ilvI under BCAA limitation.

* Corresponding author. Mailing address: 5193 Biomedical & Physical Sciences Building, Michigan State University, East Lansing, MI 48824. Phone: (517) 355-6463, ext. 1574. Fax: (517) 353-8957. E-mail: mulks{at}msu.edu.

{triangledown} Published ahead of print on 23 October 2006.

Editor: V. J. DiRita

Infection and Immunity, January 2007, p. 91-103, Vol. 75, No. 1
0019-9567/07/$08.00+0     doi:10.1128/IAI.00120-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Subashchandrabose, S., LeVeque, R. M., Wagner, T. K., Kirkwood, R. N., Kiupel, M., Mulks, M. H. (2009). Branched-Chain Amino Acids Are Required for the Survival and Virulence of Actinobacillus pleuropneumoniae in Swine. Infect. Immun. 77: 4925-4933 [Abstract] [Full Text]  


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