Reference "The macrophage-specific membrane protein Nramp controlling natural resistance to infections in mice has homologues expressed in the root system of plants"

Reference ID

276

Title

The macrophage-specific membrane protein Nramp controlling natural resistance to infections in mice has homologues expressed in the root system of plants

Source

Plant molecular biology, 1995, vol. 29, pp. 1181-1196

Authors (6)

Belouchi-A	Cellier-M
Kwan-T	Saini-H-S
Leroux-G	Gros-P

Abstract

In mice, natural resistance or susceptibility to infection with Mycobacteria,
Salmonella, and Leishmania is controlled by a gene named Bcg. Bcg regulates the
capacity of macrophages to limit intracellular replication of the ingested
parasites, and is believed to regulate a key bactericidal mechanism of this
cell. Recently, we have cloned the Bcg gene and shown that it encodes a novel
macrophage-specific membrane protein designated Nramp. A routine search of the
public databases for sequences homologous to Nramp identified 3 expressed
sequence tags (EST) that show strong similarities to the mammalian protein. We
report the identification and cloning of a full-length cDNA clone corresponding
to a plant homologue (OsNramp1) of mammalian Nramp. Predicted amino acid
sequence of the plant protein indicates a remarkable degree of similarity (60%
homology) with its mammalian counterpart, including identical number, position,
and composition of transmembrane domains, glycosylation signals, and consensus
transport motif, suggesting an identical overall secondary structure and
membrane organization for the two proteins. This high degree of structural
similarity indicates that the two proteins may be functionally related, possibly
through a common mechanism of transport. RNA hybridization studies and RT-PCR
analyses indicate that OsNramp1 mRNA is expressed primarily in roots and only at
very low levels in leaves/stem. DNA hybridization studies indicate that OsNramp1
is not a single gene, but rather forms part of a novel gene family which has
several members in all plants tested including cereals such as rice, wheat, and
corn, and also in common weed species. The striking degree of conservation
between the macrophage-specific mammalian Nramp and its OsNramp1 plant homologue
is discussed with respect to possible implications in the metabolism of nitrate
in both organisms.