Natural resistance to infection with intracellular parasites, such as Leishmania, Salmonella, and Mycobacterium, is controlled in mice by the expression of a single dominant gene locus designated Lsh/Ity/Bcg. Natural resistance-associated macrophage protein gene 1 (NRAMP1) was isolated as a candidate gene. NRAMP1 encodes an M(r) 60000 polypeptide with 10-12 potential transmembrane domains and an evolutionary conserved consensus transport motif. The present study shows that the human NRAMP1 molecule is expressed in all cell lineages of macrophage/monocyte and B- and T-lymphocytes. Immunohistochemical analysis using antihuman NRAMP1 antibody provides the direct evidence that the NRAMP1 molecule is located and distributed on the plasma membrane. An NRAMP1-glutathione S-transferase (GST) fusion protein was used to affinity-purify a protein, bound to the NH2-terminal cytoplasmic domain of NRAMP1. It was found that the NRAMP1 molecule was associated with α- and β-tubulin of microtubules. These results suggest that NRAMP1 may function as a molecule, possessing the abilities of membrane-anchoring and microtubule-binding, for the microtubule-mediated transport of vesicles and be a new class of microtubule-associated proteins.
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