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Infection and Immunity, January 1999, p. 182-186, Vol. 67, No. 1
Department of Microbiology, University of
Pennsylvania School of Medicine, Philadelphia, Pennsylvania
19104-6076
Received 12 August 1998/Returned for modification 2 October
1998/Accepted 20 October 1998
Listeria monocytogenes, a gram-positive facultative
intracellular pathogen, produces two distinct phospholipases C. PC-PLC, encoded by plcB, is a broad-range phospholipase, whereas
PI-PLC, encoded by plcA, is specific for
phosphatidylinositol. It was previously shown that PI-PLC plays a role
in efficient escape of L. monocytogenes from the primary
phagosome. To further understand the function of PI-PLC in
intracellular growth, site-directed mutagenesis of plcA was
performed. Two potential active-site histidine residues were mutated
independently to alanine, serine, and phenylalanine. With the exception
of the activity of the enzyme containing H38F, which was unstable, the
PI-PLC enzyme activities of culture supernatants containing each mutant
enzyme were <1% of wild-type activity. In addition, the levels of
expression of the mutant PI-PLC proteins were equivalent to wild-type
expression. Derivatives of L. monocytogenes containing
these specific plcA mutations were found to have phenotypes similar to that of the plcA deletion strain in an assay for
escape from the primary vacuole, in intracellular growth in a murine macrophage cell line, and in a plaquing assay for cell-to-cell spread.
Thus, catalytic activity of PI-PLC is required for all its
intracellular functions.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Mutagenesis of Active-Site Histidines of
Listeria monocytogenes Phosphatidylinositol-Specific
Phospholipase C: Effects on Enzyme Activity and Biological
Function
and
*
Corresponding author. Mailing address: Department of
Microbiology, University of Pennsylvania School of Medicine, 301C
Johnson Pavilion, Philadelphia, PA 19104-6076. Phone: (215) 898-6384. Fax: (215) 573-4856. E-mail:
goldfinh{at}mail.med.upenn.edu.
Present address: Department of Microbiology, Monash University,
Clayton 3168, Australia.
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