The frpB1 gene of Helicobacter pylori is regulated by iron and encodes a membrane protein capable of binding haem and haemoglobin

► FrpB1, a novel membrane protein, has more affinity for haem than haemoglobin. ► frpB1 mRNA levels were repressed by free iron and modulated by haem or haemoglobin. ► Haem or haemoglobin support cellular growth when frpB1 is overexpressed. ► FrpB1 3D modelling revealed the motifs necessary to bind haem or haemoglobin. FrpB1 is a novel membrane protein of Helicobacter pylori that is capable of binding both haem and haemoglobin but consistently shows more affinity for haem. The mRNA levels of frpB1 were repressed by iron and lightly modulated by haem or haemoglobin. The overexpression of the frpB1 gene supported cellular growth when haem or haemoglobin were supplied as the only iron source. Three-dimensional modelling revealed the presence of motifs necessary to bind either haem or haemoglobin. Our overall results support the idea that FrpB1 is a membrane protein of H. pylori that allows this pathogen to survive in the human stomach.