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Nramp defines a family of membrane proteins
M Cellier1, G Privé, A Belouchi
1Department of Biochemistry, McGill University, Montreal, Canada.
Abstract:
Nramp (natural resistance-associated macrophage protein) is a newly identified family of integral membrane proteins whose biochemical function is unknown. We report on the identification of Nramp homologs from the fly Drosophila melanogaster, the plant Oryza sativa, and the yeast Saccharomyces cerevisiae. Optimal alignment of protein sequences required insertion of very few gaps and revealed remarkable sequence identity of 28% (yeast), 40% (plant), and 55% (fly) with the mammalian proteins (46%, 58%, and 73% similarity), as well as a common predicted transmembrane topology. This family is defined by a highly conserved hydrophobic core encoding 10 transmembrane segments. Other features of this hydrophobic core include several invariant charged residues, helical periodicity of sequence conservation suggesting conserved and nonconserved faces for several transmembrane helices, a consensus transport signature on the intracytoplasmic face of the membrane, and structural determinants previously described in ion channels. These characteristics suggest that the Nramp polypeptides form part of a group of transporters or channels that act on as yet unidentified substrates.
Insights
Researchers identified natural resistance-associated macrophage protein (Nramp) homologs across species. These integral membrane proteins share conserved structural features, suggesting a role as transporters or channels.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Natural resistance-associated macrophage protein (Nramp) is a family of integral membrane proteins.
- The biochemical function of Nramp proteins remains largely unknown.
- Previous studies have focused on mammalian Nramp proteins.
Purpose of the Study:
- To identify and characterize Nramp homologs in diverse organisms.
- To investigate the evolutionary conservation of Nramp protein structure and function.
- To gain insights into the potential biochemical roles of Nramp proteins.
Main Methods:
- Bioinformatic analysis of protein sequences.
- Sequence alignment and homology detection.
- Prediction of transmembrane topology.
Main Results:
- Nramp homologs were identified in Drosophila melanogaster (fly), Oryza sativa (plant), and Saccharomyces cerevisiae (yeast).
- Remarkable sequence identity and similarity were found between mammalian Nramp proteins and homologs from other species.
- A conserved transmembrane topology with a hydrophobic core of 10 segments was predicted for all Nramp family members.
Conclusions:
- The Nramp family is evolutionarily conserved across a wide range of species.
- Conserved structural features, including invariant charged residues and a transport signature, suggest a functional role.
- Nramp proteins likely function as transporters or channels for unidentified substrates.