RESUMO
We report here the first identification and structural characterization of a eukaryotic protein with homology to the bacterial MgtE family of potential Mg(2+) transporters. This human protein, denoted solute carrier family 41 member 1 (SLC41A1), consists of 513 amino acids with an estimated molecular weight of 56kDa. Computer analysis of the protein structure reveals that the protein consists of 10 putative transmembrane domains and includes two distinct domains highly homologous to the integral membrane part of the bacterial MgtE protein family. The gene encoding SLC41A1 is found on chromosome 1 (1q31-32) and the protein coding sequence is found on 10 exons. A 5-kb long transcript is identified in various human tissues with highest expression levels in heart and testis. We have also identified 10 SLC41A1 homologs in Homo sapiens, Mus musculus, Drosophila melanogaster, Anopheles gambiae, and Caenorhabditis elegans, and propose that these hypothetical proteins belong to a novel eukaryotic gene family.
Assuntos
Antiporters/metabolismo , Proteínas de Bactérias/metabolismo , Magnésio/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Sequência de Aminoácidos , Animais , Antiporters/genética , Proteínas de Bactérias/genética , Proteínas de Transporte de Cátions , Linhagem Celular , Cromossomos Humanos Par 1 , DNA Complementar , Humanos , Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/classificação , Proteínas de Membrana Transportadoras/genética , Dados de Sequência Molecular , Família Multigênica , Filogenia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Alinhamento de Sequência , Distribuição TecidualRESUMO
We have identified and characterized the novel human transmembrane protein 9 (TMEM9). TMEM9 encodes a 183 amino-acid protein that contains an N-terminal signal peptide, a single transmembrane region, three potential N-glycosylation sites, and three conserved cys-rich domains in the N-terminus, but no hitherto known functional domains. The protein is highly conserved between species from Caenorhabditis elegans to man and belongs to a novel family of transmembrane proteins. The TMEM9 gene consists of at least 6 exons and is localized to chromosome 1q41. TMEM9 mRNA is expressed in a wide range of tissues and cells. COS-1 cells transfected with a TMEM9 expression plasmid gave three bands of about 28, 31, and 33kDa representing glycosylated forms of TMEM9 with a protein backbone of about 26kDa. In COS-1 cells transfected with a TMEM9-GFP expression construct,TMEM9-GFP is co-expressed with LAMP1 on late endosomes and lysosomes as well as on ER. Thus, TMEM9 is a phylogenetically conserved, widely expressed transmembrane protein with a potential, but unknown function in intracellular transport.