Surface localization of Helicobacter pylori urease and a heat shock protein homolog requires bacterial autolysis

Abstract

Helicobacter pylori is a gram-negative bacterium which causes chronic gastritis and is associated with peptic ulcer disease, gastric carcinoma, and gastric lymphoma. The bacterium is characterized by potent urease activity, thought to be located on the outer membrane, which is essential for survival at low pH. The purpose of the present study was to investigate mechanisms whereby urease and HspB, a GroEL homolog, become surface associated in vitro. Urease, HspB, and catalase were located almost exclusively within the cytoplasm in fresh log-phase cultures assessed by cryo-immunoelectron microscopy. In contrast, significant amounts of surface-associated antigen were observed in older or subcultured preparations concomitantly with the appearance of significant amounts of extracellular antigen, amorphous debris, and membrane fragments. By use of a variety of biochemical methods, a significant fraction of urease and HspB was associated with the outer membrane in subcultured preparations of H. pylori. Taken together, these results strongly suggest that H. pylori cells undergo spontaneous autolysis during culture and that urease and HspB become surface associated only concomitant with bacterial autolysis. By comparing enzyme sensitivity to flurofamide (a potent, poorly diffusible urease inhibitor) in whole cells with that in deliberately lysed cells, we show that both extracellular and intracellular urease molecules are active enzymatically. Autolysis of H. pylori is an important phenomenon to recognize since it likely exerts significant effects on the behavior of H. pylori. Furthermore, the surface properties of H. pylori must be unique in promoting adsorption of cytoplasmic proteins.

Localization of heat shock proteins in clinical Actinobacillus actinomycetemcomitans strains and their effects on epithelial cell proliferation

“…Based on our present and previous results [15], GroEL-like protein is located in the soluble cell fractions, but also found in the membrane fraction of A. actinomycetemcomitans. This is similar to the GroEL localization in Helicobacter pylori [25]. DnaK-like protein is located intracellularly in A. actinomycetemcomitans [15], Borrelia burgdorferi [26], and Escherichia coli, in which, additionally, a subpopulation of DnaK-like protein may be membrane-associated [27].…”

The GroEL-like protein from Campylobacter rectus: immunological characterization and interleukin-6 and -8 induction in human gingival fibroblast

“…Wilson and his group [14,15] showed that surface associated material (SAM) from A. actinomycetemcomitans contained the GroEL-like protein and released it extracellularly in periodontal lesion. In H. pylori, HspB (GroEL homologue) is released by bacterial autolysis and becomes adsorbed to the surface of intact bacteria in vitro, and this mechanism also seems to be present in vivo when human gastric biopsies are examined [16,17]. On the other hand, Vanet and Labigne [18] concluded that secretion of HspB did not occur by a programmed autolysis process but by a speci¢c and selective mechanism.…”

Global transcriptional profiles ofStaphylococcus aureustreated with berberine chloride

“…Urease gene clusters also encode accessory genes, in addition to these structural genes, which are required for the de novo synthesis of active urease (Beenken et al, 2004). In Helicobacter pylori, urease is expressed at very high levels, and a shift to an acidic pH may result in a significant increase in the level of ure operon mRNA (Phadnis et al, 1996). In other bacteria, the urease activity is regulated in response to environmental changes, such as changes in pH, urea and nitrogen availability, and to growth phase (Burne & Chen, 2000).…”