Nramp

(= natural resistance associated macrophage protein; Nramp1, Nramp2)

Nramp1 codes for an integral membrane protein (65 kD) expressed only in macrophages/monocytes and PMNs. Localized to endosomal/lysosomal compartment and rapidly recruited to the phagosome membrane following phagocytosis. Mutations in Nramp1 seem to abrogate the ability of macrophages to kill intracellular parasites such as Mycobacterium tuberculosis and to be associated with onset of rheumatoid arthritis. Nramp2 is very similar to Nramp1 but expressed in more tissues and is known to be an iron transporter. Yeast homologues Smf1 and Smf2 transport divalent cations.