title: The cation diffusion facilitator protein EmfA of Rhizobium etli belongs to a novel subfamily of Mn(2+)/Fe(2+) transporters conserved in α-proteobacteria.
abstract: Manganese (Mn(2+)) plays a key role in important cellular functions such as oxidative stress response and bacterial virulence. The mechanisms of Mn(2+) homeostasis are not fully understood, there are few data regarding the functional and taxonomic diversity of Mn(2+) exporters. Our recent phylogeny of the cation diffusion facilitator (CDF) family of transporters classified the bacterial Mn(2+)-CDF transporters characterized to date, Streptococcus pneumoniae MntE and Deinococcus radiodurans DR1236, into two monophyletic groups. DR1236 was shown to belong to the highly-diverse metal specificity clade VI, together with TtCzrB, a Zn(2+)/Cd(2+) transporter from Thermus thermophilus, the Fe(2+) transporter Sll1263 from Synechocystis sp and eight uncharacterized homologs whose potential Mn(2+)/Zn(2+)/Cd(2+)/Fe(2+) specificities could not be accurately inferred because only eleven proteins were grouped in this clade. A new phylogeny inferred from the alignment of 197 clade VI homologs revealed three novel subfamilies of uncharacterized proteins. Remarkably, one of them contained 91 uncharacterized α-proteobacteria transporters (46% of the protein data set) grouped into a single subfamily. The Mn(2+)/Fe(2+) specificity of this subfamily was proposed through the functional characterization of the Rhizobium etli RHE_CH03072 gene. This gene was upregulated by Mn(2+), Zn(2+), Cd(2+) and Fe(2+) but conferred only Mn(2+) resistance to R. etli. The expression of the RHE_CH03072 gene in an E. coli mntP/zitB/zntA mutant did not relieve either Zn(2+) or Mn(2+) stress but slightly increased its Fe(2+) resistance. These results indicate that the RHE_CH03072 gene, now designated as emfA, encodes for a bacterial Mn(2+)/Fe(2+) resistance CDF protein, having orthologs in more than 60 α-proteobacterial species.
authors: Programa de Ingeniería Genómica, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos, México. alex@ccg.unam.mx.
authors: Ciro
authors: C
authors: Cubillas
authors: Pablo
authors: P
authors: Vinuesa
authors: Maria Luisa
authors: ML
authors: Tabche
authors: Araceli
authors: A
authors: Dávalos
authors: Alejandra
authors: A
authors: Vázquez
authors: Ismael
authors: I
authors: Hernández-Lucas
authors: David
authors: D
authors: Romero
authors: Alejandro
authors: A
authors: García-de los Santos
mesh_terms: D020561:Alphaproteobacteria / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002413:Cations, Divalent / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D007501:Iron / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D042163:Rhizobium etli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D002413:Cations, Divalent; D008345:Manganese; D007501:Iron