Growth of Bacillus subtilis on citrate and isocitrate is supported by the Mg2+-citrate transporter CitM.
نویسندگان
چکیده
Bacillus subtilis 168 was assayed for its growth on tricarboxylic acid (TCA) cycle intermediates and related compounds as the sole carbon sources. Growth of the organism was supported by citrate, D-isocitrate, succinate, fumarate and L-malate, whereas no growth was observed in the presence of cis-aconitate,2-oxoglutarate, D-malate, oxaloacetate and tricarballylate. Growth of the organism on the tricarboxylates citrate and D-isocitrate required the presence of functional CitM, an Mg(2+)-citrate transporter, whereas its growth on succinate, fumarate and L-malate appeared to be CitM-independent. Interestingly, the naturally occurring enantiomer D-isocitrate was favoured over L-isocitrate by the organism. Like citrate, D-isocitrate was shown to be an inducer of citM expression in B. subtilis. The addition of 1 mM Mg(2+) to the growth medium improved growth of the organism on both citrate and D-isocitrate, suggesting that D-isocitrate was taken up by CitM in complex with divalent metal ions. Subsequently, the ability of CitM to transport D-isocitrate was demonstrated by competition experiments and by heterologous exchange in right-side-out membrane vesicles prepared from E. coli cells expressing citM. None of the other TCA cycle intermediates and related compounds tested were recognized by CitM. Uptake experiments using radioactive (63)Ni(2+) provided direct evidence that D-isocitrate is transported in complex with divalent metal ions.
منابع مشابه
Growth of Bacillus subtilis on citrate and isocitrate is supported by the Mg-citrate transporter CitM
Bacillus subtilis 168 was assayed for growth on TCA cycle intermediates and related compounds as sole carbon source. Growth was supported by citrate, D-isocitrate, succinate, fumarate and L-malate, whereas no growth was observed in the presence of cis-aconitate, αketoglutarate, D-malate, oxaloacetate and tricarballylate. Growth on the tricarboxylates citrate and D-isocitrate required the presen...
متن کاملSecondary transporters for citrate and the Mg(2+)-citrate complex in Bacillus subtilis are homologous proteins.
Citrate uptake in Bacillus subtilis is mediated by a secondary transporter that transports the complex of citrate and divalent metal ions. The gene coding for the transporter termed CitM was cloned, sequenced, and functionally expressed in Escherichia coli. Translation of the base sequence to the primary sequence revealed a transporter that is not homologous to any known secondary transporter. ...
متن کاملImpact of the Mg-citrate transporter CitM on heavy metal toxicity in Bacillus subtilis
Bacillus subtilis possesses a secondary transporter CitM that is specific for the complex of citrate and Mg but is also capable of transporting citrate in complex with the heavy metal ions Zn, Ni and Co. We report on the impact of CitM activity on the toxicity of the heavy metals Zn, Ni and Co + in B. subtilis. In a CitM deletion mutant or under conditions when CitM is not expressed, the toxic ...
متن کاملSecondary Transporters for Citrate and the Mg-Citrate Complex in Bacillus subtilis Are Homologous Proteins
Citrate uptake in Bacillus subtilis is mediated by a secondary transporter that transports the complex of citrate and divalent metal ions. The gene coding for the transporter termed CitM was cloned, sequenced, and functionally expressed in Escherichia coli. Translation of the base sequence to the primary sequence revealed a transporter that is not homologous to any known secondary transporter. ...
متن کاملComplementary metal ion specificity of the metal-citrate transporters CitM and CitH of Bacillus subtilis.
Citrate uptake in Bacillus subtilis is stimulated by a wide range of divalent metal ions. The metal ions were separated into two groups based on the expression pattern of the uptake system. The two groups correlated with the metal ion specificity of two homologous B. subtilis secondary citrate transporters, CitM and CitH, upon expression in Escherichia coli. CitM transported citrate in complex ...
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ورودعنوان ژورنال:
- Microbiology
دوره 148 Pt 11 شماره
صفحات -
تاریخ انتشار 2002