Frontiers in Anti-infective Agents

Volume: 2

Regulation of Haemoglobin, Haem Uptake by FrpB Family Proteins in Helicobacter pylori

Author(s): José de Jesús Olivares Trejo and Juan Mosqueda

Pp: 150-160 (11)

Doi: 10.2174/9789811469589120020009

* (Excluding Mailing and Handling)

Abstract

Helicobacter pylori is a Gram-negative spiral bacteria that has been associated with peptic ulcers, gastritis, duodenitis and it is believed to be the causative agent of gastric cancer and anemia. Its iron requirements when it infects its human host are high, therefore this bacterium has developed mechanisms to obtain iron from human sources. This human pathogen can grow in broth media using as iron source human proteins such as lactoferrin (Lf), haem and haemoglobin (Hb). However, it is still not fully understood how the process of iron acquisition occurs. An in silico analysis has shown that H. pylori has a family of three outer membrane proteins regulated by iron termed FrpB (Iron-regulated outer membrane protein). Two of them: FrpB1 and FrpB2 bind haem and FrpB1 also binds Hb. The last protein, FrpB3 has the capacity of haem-binding. The analysis by 3D model showed that three proteins are structurally conserved with the typical barrel structure inserted into the membrane. Moreover, the necessary motifs for Hb-binding have been identified. Each gene is regulated by the presence of an iron source, for instance FrpB1 is overexpressed if haem is present, while FrpB2 was induced in the presence of haem and Hb. In the case of FrpB3, it is overexpressed in the presence of free iron. It is believed that there are other proteins implicated in iron acquisition that have not been investigated yet. In summary, H. pylori secretes proteins to support the extreme environment present in the stomach. Perhaps iron helps the bacterium to resist the acidic environment of the human stomach and this mechanism is vital for H. pylori during the infection process.


Keywords: Gene Regulation, Helicobacter pylori, Haemoglobin, Haem, 3D Model.

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