Two major potassium uptake systems, KtrI and KtrII, in Enterococcus hirae

Kawano, M

doi:10.1016/s0378-1097(99)00271-2

Cited by 5 publications

(7 citation statements)

References 11 publications

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“…It has been speculated that the KtrAB system is a new two-component K ϩ transport system. As we have found a ktrA-like gene in E. hirae and Enterococcus faecalis (21), it is conceivable that the E. hirae KtrII system belongs to the KtrAB family. It is important to investigate the role of the ktrA-like gene product in NtpJ-dependent K ϩ transport activity (Fig.…”

Section: Discussionmentioning

confidence: 80%

Evidence for Na⁺Influx via the NtpJ Protein of the KtrII K⁺Uptake System inEnterococcus hirae

et al. 2000

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The ntpJ gene, a cistron located at the tail end of the vacuolar-type Na ؉ -ATPase (ntp) operon of Enterococcus hirae, encodes a transporter of the KtrII K ؉ uptake system. We found that K ؉ accumulation in the ntpJdisrupted mutant JEM2 was markedly enhanced by addition of valinomycin at pH 10. Studies of the membrane potential (⌬⌿; inside negative) by 3,3-dihexyloxacarbocyanine iodide fluorescence revealed that the ⌬⌿ was hyperpolarized at pH 10 in JEM2; the ⌬⌿ values of the parent strain ATCC 9790 and JEM2, estimated by determining the equilibrium distribution of K ؉ or Rb ؉ in the presence of valinomycin, were ؊118 and ؊160 mV, respectively. ⌬⌿ generation at pH 10 was accomplished by an electrogenic Na ؉ efflux via the Na ؉ -ATPase, whose levels in the two strains were quite similar. Na ؉ uptake driven by an artificially imposed ⌬⌿ (inside negative) was missing in JEM2, suggesting that NtpJ mediates Na ؉ movement in addition to K ؉ movement. Finally, the growth of JEM2 arrested in K ؉

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Section: Discussionmentioning

confidence: 80%

Evidence for Na⁺Influx via the NtpJ Protein of the KtrII K⁺Uptake System inEnterococcus hirae

et al. 2000

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“…Potassium is a major cytoplasmic cation in growing bacterial cells, composing 0.8-1.5% of the dry mass of the cell and plays important roles in cell physiology. It is required in activating enzymes, including those involved in protein synthesis, and in the maintenance of osmotic pressure and regulation of pH (Gerardi et al, 1994;Kawano et al, 1999). When the osmotic pressure of the medium increases, potassium ions are transferred into the cell for the adjustment of pressure.…”

Section: Cation Concentration In Sludgementioning

confidence: 99%

Monovalent cations and their influence on activated sludge floc chemistry, structure, and physical characteristics

Kara

Gürakan

Sanin

2007

Biotech & Bioengineering

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Multivalent cations have been known to be important components of activated sludge floc structure due to their bridging ability of the negatively charged sites on the biopolymer network. Recently in batch systems it was found that excess concentration of monovalent cations led to the deterioration in settleability, dewaterability of sludges and effluent quality of the system. In this study, effect of influent monovalent cations (potassium and sodium) on activated sludge floc structure was investigated in semi-continuous reactors. Results revealed that the increase in concentration of both ions correlated to the general increase in total EPS concentration. The zeta potential values were affected by the cation type and dose in such a way that sludge from sodium reactors had always higher zeta potential values (higher negative charge) than the sludges from potassium reactors. Flocs from sodium reactors were more fragile and weak and the capillary suction time values of these sludges were higher compared to those from potassium reactors. The findings of this research conclude that the floc structure is significantly weakened with the increase of monovalent cations. Even though EPS is produced, it is unable to bind the floc components together. With this, the physical properties of sludge deteriorate for both cations.

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“…Trk consists of three types of subunits: TrkE/SapD that binds ATP (7,8), TrkA that binds NAD(H) (9), and TrkG/TrkH which translocates K ϩ across the membrane (2). The third regulated bacterial K ϩ -uptake system is Ktr (4,10,11). Its activity depends on Na ϩ ions (12).…”

mentioning

confidence: 99%

ATP Binding to the KTN/RCK Subunit KtrA from the K+-uptake System KtrAB of Vibrio alginolyticus

Kröning

Willenborg²,

Tholema³

et al. 2007

Journal of Biological Chemistry

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Two major potassium uptake systems, KtrI and KtrII, in Enterococcus hirae

Cited by 5 publications

References 11 publications

Evidence for Na⁺Influx via the NtpJ Protein of the KtrII K⁺Uptake System inEnterococcus hirae

Evidence for Na⁺Influx via the NtpJ Protein of the KtrII K⁺Uptake System inEnterococcus hirae

Monovalent cations and their influence on activated sludge floc chemistry, structure, and physical characteristics

ATP Binding to the KTN/RCK Subunit KtrA from the K+-uptake System KtrAB of Vibrio alginolyticus

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Two major potassium uptake systems, KtrI and KtrII, in Enterococcus hirae

Cited by 5 publications

References 11 publications

Evidence for Na+Influx via the NtpJ Protein of the KtrII K+Uptake System inEnterococcus hirae

Evidence for Na+Influx via the NtpJ Protein of the KtrII K+Uptake System inEnterococcus hirae

Monovalent cations and their influence on activated sludge floc chemistry, structure, and physical characteristics

ATP Binding to the KTN/RCK Subunit KtrA from the K+-uptake System KtrAB of Vibrio alginolyticus

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Evidence for Na⁺Influx via the NtpJ Protein of the KtrII K⁺Uptake System inEnterococcus hirae

Evidence for Na⁺Influx via the NtpJ Protein of the KtrII K⁺Uptake System inEnterococcus hirae