Cuong Duy Tran, Hien Huynh, Fiona Campbell, Peter Coyle & Ross Butler.
Gastroenterology and Hepatology (2001), Volume 16; Supplement: A134

Asia Pacific Digestive Week 2001 incorporating Australian Gastroenterology Week, 23-27 September 2001, Sydney, Australia.

INTRODUCTION: Helicobacter pylori (Hp) is associated with gastritis, peptic ulcer disease and the development of gastric carcinoma. The pathogenesis may be associated with the ability to acquire metal ions, particularly iron. Metallothionein (MT) is a ubiquitous low molecular weight cysteine-rich, heavy metal-binding protein involved in metal homeostasis. The aim of this study was to identify metal-dependent proteins in Hp using a Cd/haemoglobin affinity assay.
METHOD: Hp (SS1 strain) was grown on Hp-selective agar plates for 48 hr, transferred into Brain Heart Infusion broth and cultured for another 24 hr. ZnSO4 or FeSO4 (2-50 mM) was added to the broth to induce MT. Bacterial numbers and protein concentrations were determined by culturing the 24 hr broth on agar plates and by an ELISA technique, respectively. Results were analyzed using ANOVA followed by Tukey's LSD and were considered to be statistically significant if p<0.05.
RESULTS: Broth containing 2 mM ZnSO4 (4.5 x 10-5 nmol Cd bound/mg protein) increased metalloprotein expression compared to controls (3 x 10-5 nmol Cd bound/mg protein) and broth with 5 mM ZnSO4 (3.6 x 10-5 nmol Cd bound/mg protein), however, broth containing higher than 10 mM ZnSO4 reduced metalloprotein levels. FeSO4 did not induce metalloprotein expression. Similar to Zn, Fe at higher concentrations (5-50 mM) inhibited the production of metal-dependent proteins. Bacterial number was either the same as control or increased at higher concentrations of Zn and Fe.
CONCLUSIONS: Zn but not Fe induced expression of a heat-stable metal-dependent protein of low molecular weight in Hp. The most probable identity of this metalloprotein is a bacterial metallothionein-like protein, however further studies are needed to characterize and determine the role of this newly described protein.