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Infection and Immunity, November 1999, p. 5587-5596, Vol. 67, No. 11
Center for Vaccine Development, Department of
Pediatrics, University of Maryland School of Medicine, Baltimore,
Maryland 21201,1 and Department of
Public Health, Faculty of Medicine, UNAM, 04510 Mexico DF,
Mexico2
Received 2 June 1999/Returned for modification 29 July
1999/Accepted 10 August 1999
We have identified and characterized a secreted protein, designated
Pic, which is encoded on the chromosomes of enteroaggregative Escherichia coli (EAEC) 042 and Shigella
flexneri 2457T. The product of the pic gene is
synthesized as a 146.5-kDa precursor molecule which is processed at the
N and C termini during secretion, allowing the release of a mature
protein (109.8 kDa) into the culture supernatant. The deduced amino
acid sequence of Pic shows high homology to autotransporter proteins,
particularly a subgroup termed the SPATEs (serine protease
autotransporters of the Enterobacteriaceae). Present in all
members of this subgroup is a motif similar to the active sites of
certain serine proteases. Pic catalyzes gelatin degradation, which can
be abolished by disruption of the predicted proteolytic active site.
Functional analysis of the Pic protein implicates this factor in
mucinase activity, serum resistance, and hemagglutination. Our data
suggest that Pic may be a multifunctional protein involved in enteric pathogenesis.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Characterization of Pic, a Secreted Protease of
Shigella flexneri and Enteroaggregative
Escherichia coli
*
Corresponding author. Mailing address: Center for
Vaccine Development, Department of Pediatrics, University of Maryland
School of Medicine, Baltimore, MD 21201. Phone: (410) 706-7376. Fax: (410) 706-6205. E-mail: ihenders{at}umaryland.edu.
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