<b>Two‐component regulatory system involved in transcriptional control of heavy‐metal homoeostasis in <i>Alcaligenes eutrophus</i></b>

Lelie, Daniël van der; Schwuchow, Tanja; Schwidetzky, Uta; Wuertz, Stefan; Baeyens, W; Mergeay, Max; Nies, Dietrich H.

doi:10.1046/j.1365-2958.1997.d01-1866.x

Cited by 105 publications

(76 citation statements)

References 29 publications

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“…The beststudied homologue, the first czcD gene reported, was initially described as having roles in sensing the substrates of the czc-CBA locus of R. eutrophus and in regulating expression of the locus (21,29). CzcCBA is a toxic divalent cation efflux antiporter whose substrates are cadmium, zinc, and cobalt; the divalent cation is exchanged for external H ϩ (22).…”

Section: Discussionmentioning

confidence: 99%

Two Types of Bacillus subtilis tetA (L) Deletion Strains Reveal the Physiological Importance of TetA(L) in K ⁺ Acquisition as well as in Na ⁺ , Alkali, and Tetracycline Resistance

et al. 2000

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The chromosomally encoded TetA(L) protein of Bacillus subtilis is a multifunctional tetracycline-metal/H ؉ antiporter that also exhibits monovalent cation/H ؉ antiport activity and a net K ؉ uptake mode. In this study, B. subtilis mutant strains JC112 and JC112C were found to be representative of two phenotypic types of tetA(L) deletion strains that are generated in the same selection. Both strains exhibited increased sensitivity to low tetracycline concentrations as expected. The mutants also had significantly reduced ability to grow in media containing low concentrations of K ؉ , indicating that the net K ؉ uptake mode is of physiological consequence; the deficit in JC112 was greater than in JC112C. JC112 also exhibited (i) greater impairment of Na ؉ -or K

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Section: Discussionmentioning

confidence: 99%

Two Types of Bacillus subtilis tetA (L) Deletion Strains Reveal the Physiological Importance of TetA(L) in K ⁺ Acquisition as well as in Na ⁺ , Alkali, and Tetracycline Resistance

et al. 2000

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“…Standard molecular genetic techniques were used (Nies et al, 1987 ;Sambrook et al, 1989). Total RNA of E. coli was isolated as published by Oelmu$ ller et al (1990), van der Lelie et al (1997) and Große et al (1999 (7552) (Blattner et al, 1997). The ybdE gene is followed by the gene pheP for a phenylalanine-specific transport system, which is probably not connected to this system.…”

Section: Methodsmentioning

confidence: 99%

The product of the ybdE gene of the Escherichia coli chromosome is involved in detoxification of silver ions

2001

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Transcription of the ybcZ-ylcA ylcBCD-ybdE region of the Escherichia coli K38 chromosome was analysed by Northern RNA-DNA hybridization, RT-PCR and primer extension. Transcription of a dicistronic ybcZ-ylcA mRNA and a tetracistronic ylcBCD-ybdE mRNA was induced by silver and was initiated from the sigma-70 promoters ylcAp and ylcBp. Expression of β-galactosidase activity from a Φ(ylcBp-lacZ) operon fusion was also induced by Ag M and Cu 2M , but not by Zn 2M . In-frame deletion of ybdE from the chromosome yielded a silversensitive E. coli mutant strain which did not differ in its copper resistance from its wild-type strain. On the other hand, deletion of the copA gene for the copper-exporting P-type ATPase CopA resulted in copper sensitivity, but not in silver sensitivity. A ∆ybdE ∆copA double mutant strain behaved towards copper as the ∆copA strain and towards silver as the ∆ybdE strain. Thus, in E. coli, the YlcBCD-YbdE system may be involved in silver-but not in copper resistance, and CopA may be involved in copper-but not in silver resistance.

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“…Besides the CzcR and CzcS regulatory proteins (37), the membrane-bound CzcD, possibly a sensor protein, is essential for induction of czc (23). CzcD belongs to the newly coined CDF (cation diffusion facilitator) family (27).…”

mentioning

confidence: 99%

New functions for the three subunits of the CzcCBA cation-proton antiporter

Rensing¹,

Pribýl²,

Nies³

1997

J Bacteriol

121

107

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The membrane-bound CzcCBA protein complex mediates heavy metal resistance in Alcaligenes eutrophus by an active cation efflux mechanism driven by cation-proton antiport. The CzcA protein alone is able to mediate weak resistance to zinc and cobalt and is thus the central antiporter subunit. The two histidine-rich motifs in the CzcB subunit are not essential for zinc resistance; however, deletion of both motifs led to a small but significant loss of resistance to this cation. Translation of the czcC gene encoding the third subunit of the CzcCBA complex starts earlier than predicted, and CzcC is probably a periplasmic protein, as judged by the appearance of two bands after expression of czcC in Escherichia coli under control of the phage T7 promoter. Fusions of CzcC and CzcB with alkaline phosphatase and ␤-galactosidase are in agreement with a periplasmic location of most parts of both proteins. Both CzcC and CzcB are bound to a membrane, probably the outer membrane, by themselves and do not need either CzcA or each other as an anchoring protein. Based on these data, a new working model for the function of the Czc system is discussed.Alcaligenes eutrophus CH34 contains at least seven heavy metal resistance determinants, located either on the bacterial chromosome or on one of the two indigenous plasmids pMOL28 (163 kb) and pMOL30 (238 kb) (9,15,17,19,20). One of them, the czc determinant of plasmid pMOL30, mediates inducible resistance to Co 2ϩ , Zn 2ϩ , and Cd 2ϩ in A. eutrophus CH34 (21). The products of the genes czcA, czcB, and czcC form a membrane-bound protein complex catalyzing an energy-dependent efflux of these three metal cations (25,26). The mechanism of action of CzcCBA is that of a cation-proton antiporter (24).Besides the CzcR and CzcS regulatory proteins (37), the membrane-bound CzcD, possibly a sensor protein, is essential for induction of czc (23). CzcD belongs to the newly coined CDF (cation diffusion facilitator) family (27). The function of the products of additional czc genes located upstream of the czcCBA structural gene region remains unclear (37).In an old working model (22,27), CzcA may function as a cation-proton antiporter and CzcB may function as a cationbinding subunit; both subunits together form the Zn 2ϩ efflux system. The CzcC protein acts as a modifier extending the substrate specificity to Co 2ϩ and Cd 2ϩ . This model is based on computer-assisted predictions of the secondary structure and membrane orientation of the three proteins CzcA, CzcB, and CzcC and on the analysis of deletion mutants (25). In this study, we reinvestigated the function and localization of the three subunits by using more sophisticated approaches, and here we propose a new working model. MATERIALS AND METHODSBacterial strains, plasmids, and growth conditions. A. eutrophus AE104 (17) is a metal-sensitive, plasmid-free derivative of strain CH34. Escherichia coli K38(pGP1-2) (36) was used for expression of czcCBAD derivatives under control of the phage T7 promoter as described previously (19). The other bacteria...

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Two‐component regulatory system involved in transcriptional control of heavy‐metal homoeostasis in Alcaligenes eutrophus

Cited by 105 publications

References 29 publications

Two Types of Bacillus subtilis tetA (L) Deletion Strains Reveal the Physiological Importance of TetA(L) in K ⁺ Acquisition as well as in Na ⁺ , Alkali, and Tetracycline Resistance

Two Types of Bacillus subtilis tetA (L) Deletion Strains Reveal the Physiological Importance of TetA(L) in K ⁺ Acquisition as well as in Na ⁺ , Alkali, and Tetracycline Resistance

The product of the ybdE gene of the Escherichia coli chromosome is involved in detoxification of silver ions

New functions for the three subunits of the CzcCBA cation-proton antiporter

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Two‐component regulatory system involved in transcriptional control of heavy‐metal homoeostasis in Alcaligenes eutrophus

Cited by 105 publications

References 29 publications

Two Types of Bacillus subtilis tetA (L) Deletion Strains Reveal the Physiological Importance of TetA(L) in K + Acquisition as well as in Na + , Alkali, and Tetracycline Resistance

Two Types of Bacillus subtilis tetA (L) Deletion Strains Reveal the Physiological Importance of TetA(L) in K + Acquisition as well as in Na + , Alkali, and Tetracycline Resistance

The product of the ybdE gene of the Escherichia coli chromosome is involved in detoxification of silver ions

New functions for the three subunits of the CzcCBA cation-proton antiporter

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Two Types of Bacillus subtilis tetA (L) Deletion Strains Reveal the Physiological Importance of TetA(L) in K ⁺ Acquisition as well as in Na ⁺ , Alkali, and Tetracycline Resistance

Two Types of Bacillus subtilis tetA (L) Deletion Strains Reveal the Physiological Importance of TetA(L) in K ⁺ Acquisition as well as in Na ⁺ , Alkali, and Tetracycline Resistance