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.
