Complementary Metal Ion Specificity of the Metal-Citrate Transporters CitM and CitH of
            <i>Bacillus subtilis</i>

Krom, Bastiaan P.; Warner, Jessica B.; Konings, Wil N.; Lolkema, Juke S.

doi:10.1128/jb.182.22.6374-6381.2000

Cited by 67 publications

(79 citation statements)

References 33 publications

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“…The E. faecalis cluster contains both an OAD type and a malic enzyme type of decarboxylase. The transporter associated with the pathway in the Firmicutes is from the [st301]CITM transporter family in structural class ST [3] (65,66). The citrate fermentation-associated genes in the spirochete T. denticola are fragmented into three parts.…”

Section: Physiological Functionmentioning

confidence: 99%

The 2-Hydroxycarboxylate Transporter Family: Physiology, Structure, and Mechanism

Sobczak

Lolkema

2005

Microbiol Mol Biol Rev

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SUMMARY The 2-hydroxycarboxylate transporter family is a family of secondary transporters found exclusively in the bacterial kingdom. They function in the metabolism of the di- and tricarboxylates malate and citrate, mostly in fermentative pathways involving decarboxylation of malate or oxaloacetate. These pathways are found in the class Bacillales of the low-CG gram-positive bacteria and in the gamma subdivision of the Proteobacteria. The pathways have evolved into a remarkable diversity in terms of the combinations of enzymes and transporters that built the pathways and of energy conservation mechanisms. The transporter family includes H+ and Na+ symporters and precursor/product exchangers. The proteins consist of a bundle of 11 transmembrane helices formed from two homologous domains containing five transmembrane segments each, plus one additional segment at the N terminus. The two domains have opposite orientations in the membrane and contain a pore-loop or reentrant loop structure between the fourth and fifth transmembrane segments. The two pore-loops enter the membrane from opposite sides and are believed to be part of the translocation site. The binding site is located asymmetrically in the membrane, close to the interface of membrane and cytoplasm. The binding site in the translocation pore is believed to be alternatively exposed to the internal and external media. The proposed structure of the 2HCT transporters is different from any known structure of a membrane protein and represents a new structural class of secondary transporters.

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Section: Physiological Functionmentioning

confidence: 99%

The 2-Hydroxycarboxylate Transporter Family: Physiology, Structure, and Mechanism

Sobczak

Lolkema

2005

Microbiol Mol Biol Rev

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“…This mechanism has been observed for ligands with established biological functions and their own specialised channels or transporters. [27,28] For example, for some bacteria, citrate, which can be used as a carbon source, [29,30] is taken up by citrate transporters (e.g. CitM and CitH).…”

Section: Introductionmentioning

confidence: 99%

When are metal complexes bioavailable?

Zhao¹,

Campbell²,

Wilkinson³

2016

Environ. Chem.

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Environmental context. The concentration of a free metal cation has proved to be a useful predictor of metal bioaccumulation and toxicity, as represented by the free ion activity and biotic ligand models. However, under certain circumstances, metal complexes have been shown to contribute to metal bioavailability. In the current mini-review, we summarise the studies where the classic models fail and organise them into categories based on the different uptake pathways and kinetic processes. Our goal is to define the limits within which currently used models such as the biotic ligand model (BLM) can be applied with confidence, and to identify how these models might be expanded.Abstract. Numerous data from studies over the past 30 years have shown that metal uptake and toxicity are often best predicted by the concentrations of free metal cations, which has led to the development of the largely successful free-ion activity model (FIAM) and biotic ligand model (BLM). Nonetheless, some exceptions to these classical models, showing enhanced metal bioavailability in the presence of metal complexes, have also been documented, although it is not yet fully understood to what extent these exceptions can or should be generalised. Only a few studies have specifically measured the bioaccumulation or toxicity of metal complexes while carefully measuring or controlling metal speciation. Fewer still have verified the fundamental assumptions of the classical models, especially when dealing with metal complexes. In the current paper, we have summarised the exceptions to classical models and categorised them into five groups based on the fundamental uptake pathways and kinetic processes. Our aim is to summarise the mechanisms involved in the interaction of metal complexes with organisms and to improve the predictive capability of the classic models when dealing with complexes.

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“…As could be expected, several stress proteinencoding genes were included, as well as other genes involved in carbohydrate metabolism. Of particular interest was the fivefold increase in citM gene expression, since citM encodes a divalent cation/citrate symporter (31,34,52). The increase in citM mRNA was confirmed by Northern blot analysis (Fig.…”

Section: Resultsmentioning

confidence: 74%

“…Previous studies failed to clarify the basis for the extreme Co 2ϩ sensitivity of JC112 (51). The microarray experiments revealed up-regulation in JC112 of citM, which is capable of taking up citrate in complex with a number of divalent cations, including toxic divalent cations such as Co 2ϩ (31,33). We hypothesized that up-regulation of citM in JC112 could facilitate use of citrate to offset the reduced use of malate caused by the down-regulation of maeN, since the Spiz-KM medium used routinely in growth experiments contained both malate and citrate.…”

Section: Resultsmentioning

confidence: 99%

Adaptive Gene Expression in Bacillus subtilis Strains Deleted for tetL

et al. 2006

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The growth properties of a new panel of Bacillus subtilis tetL deletion strains and of a derivative set of strains in which tetL is restored to the chromosome support earlier indications that deletion of tetL results in a range of phenotypes that are unrelated to tetracycline resistance. These phenotypes were not reversed by restoration of a tetL gene to its native locus and were hypothesized to result from secondary mutations that arise when multifunctional tetL is deleted. Such genetic changes would temper the alkali sensitivity and Na ؉ sensitivity that accompany loss of the monovalent cation/proton activity of TetL. Microarray comparisons of the transcriptomes of wild-type B. subtilis, a tetL deletion strain, and its tetL-restored derivative showed that 37 up-regulated genes and 13 down-regulated genes in the deletion strain did not change back to wild-type expression patterns after tetL was returned to the chromosome. Up-regulation of the citM gene, which encodes a divalent metal ion-coupled citrate transporter, was shown to account for the Co 2؉ -sensitive phenotype of tetL mutants. The changes in expression of citM and genes encoding other ion-coupled solute transporters appear to be adaptive to loss of TetL functions in alkali and Na ؉ tolerance, because they reduce Na ؉ -coupled solute uptake and enhance solute uptake that is coupled to H ؉ entry.

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Complementary Metal Ion Specificity of the Metal-Citrate Transporters CitM and CitH of Bacillus subtilis

Cited by 67 publications

References 33 publications

The 2-Hydroxycarboxylate Transporter Family: Physiology, Structure, and Mechanism

The 2-Hydroxycarboxylate Transporter Family: Physiology, Structure, and Mechanism

When are metal complexes bioavailable?

Adaptive Gene Expression in Bacillus subtilis Strains Deleted for tetL

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