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Journal of Bacteriology, October 2001, p. 5659-5667, Vol. 183, No. 19
Department of Microbiology, University of
Minnesota Medical School, Minneapolis, Minnesota 55455
Received 18 December 2000/Accepted 12 June 2001
Pheromone-inducible aggregation substance (AS) proteins of
Enterococcus faecalis are essential for high-efficiency
conjugation of the sex pheromone plasmids and also serve as virulence
factors during host infection. A number of different functions have
been attributed to AS in addition to bacterial cell aggregation,
including adhesion to host cells, adhesion to fibrin, increased cell
surface hydrophobicity, resistance to killing by polymorphonuclear
leukocytes and macrophages, and increased vegetation size in an
experimental endocarditis model. Relatively little information is
available regarding the structure-activity relationship of AS. To
identify functional domains, a library of 23 nonpolar 31-amino-acid
insertions was constructed in Asc10, the AS encoded by the plasmid
pCF10, using the transposons TnlacZ/in and
TnphoA/in. Analysis of these insertions revealed a domain
necessary for donor-recipient aggregation that extends further into the
amino terminus of the protein than previously reported. In addition,
insertions in the C terminus of the protein also reduced aggregation.
As expected, the ability to aggregate correlates with efficient plasmid
transfer. The results also indicated that an increase in cell surface
hydrophobicity resulting from AS expression is not sufficient to
mediate bacterial aggregation.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.19.5659-5667.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Analysis of Functional Domains of the
Enterococcus faecalis Pheromone-Induced Surface Protein
Aggregation Substance
*
Corresponding author. Mailing address: Department of
Microbiology, University of Minnesota Medical School, 1420 Delaware St. SE, Minneapolis, MN 55455. Phone: (612) 625-9930. Fax: (612) 626-0623. E-mail: gary-d{at}biosci.cbs.umn.edu.
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