Reference "Cloning and characterization of the OsNramp family from Oryza sativa, a new family of membrane proteins possibly implicated in the transport of metal ions"

Reference ID

277

Title

Cloning and characterization of the OsNramp family from Oryza sativa, a new family of membrane proteins possibly implicated in the transport of metal ions

Source

Plant molecular biology, 1997, vol. 33, pp. 1085-1092

Authors (3)

Belouchi-A	Kwan-T
Gros-P

Abstract

The mammalian Nramp1 protein is an integral membrane protein expressed
exclusively in macrophages, where it plays a critical role in the ability of
these cells to destroy ingested microbes. The bactericidal mechanism of action
of Nramp1 remains unknown. We report the identification and characterization of
cDNA clones corresponding to three homologues of the mammalian Nramp1 gene from
the genome of Oryza sativa, OsNramp1, OsNramp2, and OsNramp3. These three genes
encode a novel group of highly similar hydrophobic polypeptides sharing between
64% and 75% sequence similarity, that show similar hydropathy profiles, and
predicted secondary structure, including the same number, position, and
sequence characteristics (including conserved charges) of transmembrane
domains. Together, these define a highly conserved membrane associated
hydrophobic core. The three plant proteins show a remarkable degree of sequence
similarity with their mammalian counterpart (60% to 70% similarity), including
primary and secondary structure elements previously described in ion
transporters and channels. Expression studies in normal plant tissues indicate
that while OsNramp1 is expressed primarily in roots, and OsNramp2 is primarily
expressed in leaves, OsNramp3 is expressed in both tissues. The recent
discovery that the yeast Nramp homologue SMF1 functions as a manganese
transporter raises the exciting possibility that OsNramp encodes a family of
metal ion transporters in plants.