HarA is a heme-binding NEAT-domain (NEAr Transporter, pfam05031) protein which has been shown to bind to the haptoglobin-hemoglobin complex in order to extract heme from it. HarA has also been reported to bind hemoglobin directly. HarA (also known as IsdH) contains three NEAT domains as well as a sortase A C-terminal signal for localization to the cell wall. The heme bound at the third of these NEAT domains has been shown to be transferred to the IsdA protein also localized at the cell wall, presumably through an additional specific protein-protein interaction. Haptoglobin is a hemoglobin carrier protein involved in scavenging hemoglobin in the blood following red blood cell lysis and targetting it to the liver.
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