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Infect Immun, March 1998, p. 1023-1027, Vol. 66, No. 3
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Evidence for Specific Secretion Rather than Autolysis in the Release of Some Helicobacter pylori Proteins

Anne Vanetdagger and Agnès Labigne*

Unité de Pathogénie Bactérienne des Muqueuses, Institut Pasteur, 75724 Paris Cedex 15, France

Received 29 August 1997/Returned for modification 4 November 1997/Accepted 30 December 1997

We investigated whether Helicobacter pylori cells actively secrete proteins such as the urease subunits UreA and UreB and the GroES and GroEL homologs HspA and HspB or whether these proteins were present in the extracellular compartment as a consequence of autolysis. Using a subcellular fractionation approach associated with quantitative Western blot analyses, we showed that the supernatant protein profiles were very different from those of the cell pellets, even for bacteria harvested in the late growth phase; this suggests that the release process is selective. A typical cytoplasmic protein, a beta -galactosidase homolog, was found exclusively associated with the pellet of whole-cell extracts, and no traces were found in the supernatant. In contrast, UreA, UreB, HspA, and HspB were mostly found in the pellet but significant amounts were also present in the supernatant. HspA and UreB were released into the supernatant at the same rate throughout the growth phase (3%), whereas large portions of HspB and UreA were released during the stationary phase (over 30 and 20%, respectively) rather than during the early growth phase (20% and 6, respectively). The profiles of protein obtained after water extraction of the bacteria with those of the proteins naturally released within the liquid culture supernatants demonstrated that water extraction led to the release of a large amount of protein due to artifactual lysis. Our data support the conclusion that a specific and selective mechanism(s) is involved in the secretion of some H. pylori antigens. A programmed autolysis process does not seem to make a major contribution.

* Corresponding author. Mailing address: Unité de Pathogénie Bactérienne des Muqueuses, Institut Pasteur, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France. Phone: 33 1 40 61 32 73. Fax: 33 1 40 61 36 40. E-mail: alabigne{at}pasteur.fr.

dagger Present address: Institut de Biologie Physico-Chimique, UPR 9073 du C.N.R.S., 75005 Paris, France.




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