Iron uptake by Neisseria meningitidis

In the human body, extracellular iron is bound by two chelating glycoproteins, transferrin (Tf) and lactoferrin (Lf). Neisseria meningitidis shows a strategy based on the synthesis of outer membrane receptors able to trap chelating glycoproteins and obtain iron from them directly. The 3 or 4 g of iron in an adult human body are, to a great extent, located intracellularly, either in haemoglobin (around 2.5 g) or in the proteins ferritin and haemosiderin. The small quantity of extracellular iron is chiefly bound to two transport proteins with a very high affinity for iron, Tf and Lf; iron released into the extracellular fluid as haem is complexed by haemopexin and transferred to the liver.