Cloning and functional characterization of a superfamily of microbial inwardly rectifying potassium channels

Sun, Si; Gan, Jo Han; Paynter, Jennifer J.; Tucker, Stephen J.

doi:10.1152/physiolgenomics.00026.2006

Cited by 18 publications

(30 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Each of the K ϩ transport systems Trk1, Trk2, GlnQHMP, and Kch was tested for its role in K ϩ uptake by complementing the E. coli strain TK2420 with these systems. E. coli TK2420 is a wellestablished model organism to characterize K ϩ transporters because of its lack of constitutive transporters and inability to transport K ϩ (31,(61)(62)(63). We observed that complementing E. coli TK2420 with Trk1, Trk2, or GlnQHMP facilitated significant K ϩ acquisition and enabled normal growth in low K ϩ concentrations and under stress conditions imposed by high salt concentrations and low pH.…”

Section: Discussionmentioning

confidence: 95%

Trk2 Potassium Transport System in Streptococcus mutans and Its Role in Potassium Homeostasis, Biofilm Formation, and Stress Tolerance

et al. 2016

View full text Add to dashboard Cite

Potassium (K؉ ) is the most abundant cation in the fluids of dental biofilm. The biochemical and biophysical functions of K ؉ and a variety of K ؉ transport systems have been studied for most pathogenic bacteria but not for oral pathogens. In this study, we establish the modes of K ؉ acquisition in Streptococcus mutans and the importance of K ؉ homeostasis for its virulence attributes. The S. mutans genome harbors four putative K ؉ transport systems that included two Trk-like transporters (designated Trk1 and Trk2), one glutamate/K ؉ cotransporter (GlnQHMP), and a channel-like K ؉ transport system (Kch). Mutants lacking Trk2 had significantly impaired growth, acidogenicity, aciduricity, and biofilm formation. [K ؉ ] less than 5 mM eliminated biofilm formation in S. mutans. The functionality of the Trk2 system was confirmed by complementing an Escherichia coli TK2420 mutant strain, which resulted in significant K ؉ accumulation, improved growth, and survival under stress. Taken together, these results suggest that Trk2 is the main facet of the K ؉ -dependent cellular response of S. mutans to environment stresses. IMPORTANCEBiofilm formation and stress tolerance are important virulence properties of caries-causing Streptococcus mutans. To limit these properties of this bacterium, it is imperative to understand its survival mechanisms. Potassium is the most abundant cation in dental plaque, the natural environment of S. mutans. K ؉ is known to function in stress tolerance, and bacteria have specialized mechanisms for its uptake. However, there are no reports to identify or characterize specific K ؉ transporters in S. mutans. We identified the most important system for K ؉ homeostasis and its role in the biofilm formation, stress tolerance, and growth. We also show the requirement of environmental K ؉ for the activity of biofilm-forming enzymes, which explains why such high levels of K ؉ would favor biofilm formation. Bacteria utilize specialized endogenous mechanisms to survive and proliferate in transient environments. A common bacterial response to environmental perturbations, such as acid stress, osmotic tension, and nutrient deprivation, is to accumulate certain solutes, such as potassium (K ϩ ). K ϩ , a naturally abundant cation, is present in all types of cells and is essential for both cell survival and physiology. K ϩ accumulation under stress conditions enables organisms to contend with dehydration, membrane damage, regulation of the Na ϩ /H ϩ -dependent cell energetics, and pH homeostasis while simultaneously minimizing interference with the structures and functions of intracellular proteins (1-3).In prokaryotes, four main K ϩ transport systems have been identified, which include the proteins Trk (or Ktr), Kdp, Kup, and channel-like Kch (4), all of which have different K ϩ affinities. Their variety and independent functioning have likely evolved as a cell survival strategy to ensure that adequate levels of K ϩ are present at all times to contend with environmental changes (5). These systems are r...

show abstract

Section: Discussionmentioning

confidence: 95%

Trk2 Potassium Transport System in Streptococcus mutans and Its Role in Potassium Homeostasis, Biofilm Formation, and Stress Tolerance

et al. 2016

View full text Add to dashboard Cite

show abstract

“…These strains cannot grow on a media with low (1-10 mM) potassium (28), but expression of potassium channels or transporters can restore their growth (29). This strategy was successful for isolation of potassium channels and transporters (30) as well as the mutations that activate potassium channels (31,32). A similar approach but utilizing the Saccharomyces cerevisiae K ϩ transport-deficient mutant was also used to study functional substitutions in the Kir2.1 inwardly rectifying potassium channel (33).…”

mentioning

confidence: 99%

Genetic Screen for Potassium Leaky Small Mechanosensitive Channels (MscS) in Escherichia coli

Koprowski

Grajkowski

Isacoff

et al. 2011

Journal of Biological Chemistry

View full text Add to dashboard Cite

Mechanosensitive membrane channels in bacteria respond to the mechanical stretching of the membrane. They will open when bacteria are subjected to rapid osmotic down shock. MscS is a bacterial mechanosensitive channel of small conductance. It is a heptameric membrane protein whose transmembrane part, including the gate and its kinetics, has been well characterized. MscS has a large cytoplasmic domain of a cage-like shape that changes its conformation upon gating, but its involvement in gating is not understood. We screened MscS for mutations that cause potassium leak in Escherichia coli strains deficient in potassium transport systems. We did a phenotypic analysis of single and multiple mutants and recorded the single channel activities of some of them. After these analyses, we attributed the effects of a number of mutations to particular functional states of the channel. Our screen revealed that MscS leaks potassium in a desensitized and in an inactivated state. It also appeared that the lower part of TM3 (transmembrane, pore-forming helix) and the cytoplasmic ␤ domain are tightly packed in the inactivated state but are dissociated in the open state. We attribute the TM3-␤ interaction to stabilization of the inactivated state in MscS and to the control of tight closure of its membrane pore.

show abstract

“…Instead, the dominant lipids are phosphatidylethanolamines (PE), and phosphatidylglycerols (PG), 20 in which KirBac channels are active. 11,21 As eukaryotic organisms evolved, PIP 2 and other acidic lipids became increasingly concentrated in plasmalemmal membranes. The unwonted inhibitory effect of PIP 2 on KirBac1.1 activity is such that at the predicted PIP 2 concentrations in mammalian membranes (~1% of phospholipids), 22,23 KirBac-based channel activity would be completely suppressed.…”

mentioning

confidence: 99%

Lipids driving protein structure? Evolutionary adaptations in Kir channels

D’Avanzo¹,

Cheng²,

Wang³

et al. 2010

Channels

View full text Add to dashboard Cite

Many eukaryotic channels, transporters and receptors are activated by phosphatidyl inositol bisphosphate (PIP2) in the membrane, and every member of the eukaryotic inward rectifier potassium (Kir) channel family requires membrane PIP2 for activity. In contrast, a bacterial homolog (KirBac1.1) is specifically inhibited by PIP2. We speculate that a key evolutionary adaptation in eukaryotic channels is the insertion of additional linkers between trans-membrane and cytoplasmic domains, revealed by new crystal structures, that convert PIP2 inhibition to activation. Such an adaptation may reflect a novel evolutionary drive to protein structure,; one that was necessary to permit channel function within the highly negatively charged membranes that evolved in the eukaryotic lineage.

show abstract

Cloning and functional characterization of a superfamily of microbial inwardly rectifying potassium channels

Abstract: Cloning and functional characterization of a superfamily of microbial inwardly rectifying potassium channels.

Cited by 18 publications

References 20 publications

Trk2 Potassium Transport System in Streptococcus mutans and Its Role in Potassium Homeostasis, Biofilm Formation, and Stress Tolerance

Trk2 Potassium Transport System in Streptococcus mutans and Its Role in Potassium Homeostasis, Biofilm Formation, and Stress Tolerance

Genetic Screen for Potassium Leaky Small Mechanosensitive Channels (MscS) in Escherichia coli

Lipids driving protein structure? Evolutionary adaptations in Kir channels

Contact Info

Product

Resources

About