CHR, a Novel Family of Prokaryotic Proton Motive Force-Driven Transporters Probably Containing Chromate/Sulfate Antiporters

Nies, Dietrich H.; Koch, Sandra; Wachi, Shinichiro; Peitzsch, Nicola; Saier, Milton H.

doi:10.1128/jb.180.21.5799-5802.1998

Cited by 95 publications

(61 citation statements)

References 31 publications

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“…Although bootstrap supporting values were relatively low, all resulting trees were similar, regardless of the algorithms employed to perform the phylogenetic analysis. This pattern suggests that bulk LCHR proteins conform to a monophyletic group, and agrees with the proposal that the origin of bidomain LCHR proteins was an ancient duplication followed by a gene fusion of two ancestral monodomain CHRs [3,8].…”

Section: ): (A)supporting

confidence: 89%

“…The C. metallidurans ChrA protein (from the LCHR2 subfamily) has been reported to have 10 TMSs, with the amino and carboxyl terminal domains similarly oriented with respect to the membrane axis [8]. By contrast, the P. aeruginosa ChrA protein (from the LCHR5 subfamily) was found to possess a 13 TMS arrangement, with the amino and carboxyl terminal domains oppositely oriented [13].…”

Section: Membrane Topology Of Schr Proteinsmentioning

confidence: 99%

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Phylogenetic analysis of the chromate ion transporter (CHR) superfamily

et al. 2007

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Because toxic heavy metals (including chromium) have been abundant on the Earth since the beginning of life, microbes have been exposed to them for nearly four billion years [1]. In response, cells have developed diverse mechanisms that confer heavy metal resistance, such as, for example, the active extrusion of toxic metal cations [2,3]. This constitutes one of the beststudied bacterial mechanisms of resistance to chromium, which is based on the active efflux of chromate driven by the membrane potential [4,5] ChrA is a membrane protein that confers resistance to the toxic ion chromate through the energy-dependent chromate efflux from the cytoplasm. In the protein databases, ChrA is a member of the chromate ion transporter (CHR) superfamily, composed of at least several dozens of members, distributed in the three domains of life. The aim of this work was to perform a phylogenetic analysis of the CHR superfamily. An exhaustive search for ChrA homologous proteins was carried out at the National Center for Biotechnology Information database. One hundred and thirty-five sequences were identified as members of the CHR superfamily [77 long-chain sequences, or bidomains (LCHR), and 58 short-chain sequences, or monodomains (SCHR)], organized mainly as tandem pairs of genes whose resultant proteins probably possess oppositely oriented membrane topology. LCHR sequences were split into amino and carboxyl domains, and the resultant domains were aligned with the SCHR proteins. A phylogenetic tree was reconstructed using four different methods, obtaining similar results. The domains were grouped into three clusters: the SCHR proteins cluster, the amino domain cluster of LCHR proteins and the carboxyl domain cluster of LCHR proteins. These results, as well as differences in the genomic context of CHR proteins, enabled the proteins to be sorted into two families (SCHR and LCHR), and 10 subfamilies. Evidence was found suggesting an ancient origin of LCHR proteins from the fusion of two SCHR protein-encoding genes; however, some secondary events of fusion and fission may have occurred later. The separate distribution of the LCHR and SCHR proteins, differences in the genomic context in both groups and the fact that chromate transport has been demonstrated only in LCHR proteins suggest that the CHR proteins comprise two or more paralogous groups in the CHR superfamily.Abbreviations CHR, chromate ion transporter; ME, minimum evolution; MP, maximum parsimony; NJ, neighbour joining; TMS, transmembrane segment; UPGMA, unweighted pair-group method using arithmetic averages.

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Section: ): (A)supporting

confidence: 89%

Section: Membrane Topology Of Schr Proteinsmentioning

confidence: 99%

Phylogenetic analysis of the chromate ion transporter (CHR) superfamily

et al. 2007

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“…With these data, the topology of the first half of P. aeruginosa ChrA, composed of six TMS, was shown to be different from that reported for the amino terminus of its C. metallidurans homolog, with only four TMS in this protein half. Comparison of reporter enzyme activities between fusions from the two ChrA proteins shows that Phe69 from Pseudomonas ChrA yielded a high PhoA value (Aguilera et al, 2004), whereas Thr60 in the Cupriavidus protein showed high LacZ (Nies et al, 1998). These data confirm a different topology for the first 70 amino acids at the N-terminal part of the two transporters.…”

Section: Discussionmentioning

confidence: 65%

“…Fourteen-TMS proteins from the MFS contain two extra TMS in the middle of the two 6-TMS primordial domains (Paulsen et al, 1996;Pao et al, 1998). Opposite examples have been reported for the already mentioned ChrA homolog from C. metallidurans (Nies et al, 1998) and for members of the OLF (oligosaccharidyl-lipid flippase) family (Hrovup et al, 2003). These proteins seem to have evolved from 12-TMS to 10-TMS polypeptides by the substitution of hydrophobic amino acids with hydrophilic residues (Nies et al, 1998;Hrovup et al, 2003).…”

Section: Discussionmentioning

confidence: 95%

Membrane topology of the chromate transporter ChrA ofPseudomonas aeruginosa

Jiménez-Mejía

Campos-Garcı́a

Cervantes

2006

FEMS Microbiology Letters

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The membrane topology of the plasmid-encoded Pseudomonas aeruginosa ChrA protein, which effluxes chromate ions, was determined by the analysis of translational fusions with reporter enzymes alkaline phosphatase and beta-galactosidase. A novel 13-TMS (transmembrane segments) topology, with the N-terminus located in the cytoplasm and the C-terminus in the periplasmic space, was consistent with the enzyme activities determined in both Escherichia coli and P. aeruginosa. Alignment of the two halves of ChrA showed significant sequence homology, with TMS I, II, III, IV, V and VI displaying similarity to TMS VIII, IX, X, XI, XII and XIII, respectively, although with opposite membrane orientations. This suggests that ChrA arose from the duplication of a gene encoding a 6-TMS ancestral protein, followed by the insertion of extra TMS VII. These data also suggest that the two halves of ChrA may carry out distinct functions for the transport of chromate.

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“…A ChrA homolog, also conferring chromate resistance, was found in an Alcaligenes eutrophus plasmid [2]. Several putative homologs have also been found in bacterial complete genome sequences [3,4]. Chromate tolerance conferred by the ChrA protein was associated to diminished accumulation of 51 CrO 23 4 [1,2].…”

Section: Introductionmentioning

confidence: 99%