Helicobacter pylori secretes the chaperonin GroEL (HSP60), which binds iron

• H. pylori can use several iron sources.
• This bacterium secretes an iron-binding protein, which we purified by haem-affinity chromatography.
• We identify the protein as the chaperonin HpGroEL, and show that it specifically binds iron and no other metals.
• HpGroEL purified from cytoplasm is also capable of binding iron.

Helicobacter pylori is a bacterium that can use multiple iron sources. However, it is unknown whether this bacterium secretes molecules such as siderophores or haemophores to scavenge iron. Here, we report the first secreted iron-binding protein of H. pylori, which we purified by haem-affinity chromatography. Mass spectrometry analysis revealed its identity as chaperonin (HpGroEL). When we compared HpGroEL with EcGroEL from Escherichia coli, they were homologous, showing 60% similarity. Additionally, purified cytoplasmic HpGroEL could also bind iron. Perhaps H. pylori secretes HpGroEL to maintain the appropriate folding of extracellular proteins and to bind iron.