A Hydrophobic Filter Confers the Cation Selectivity of Zygosaccharomyces rouxii Plasma-Membrane Na+/H+ Antiporter

2015 ◽  
Vol 427 (8) ◽  
pp. 1681-1694 ◽  
Author(s):  
Olga Kinclova-Zimmermannova ◽  
Pierre Falson ◽  
Denis Cmunt ◽  
Hana Sychrova
Keyword(s):  
Plasma Membrane ◽  
Zygosaccharomyces Rouxii ◽  
Cation Selectivity

scholarly journals Characterization of the R162W Kir7.1 mutation associated with snowflake vitreoretinopathy

2013 ◽  
Vol 304 (5) ◽  
pp. C440-C449 ◽  
Author(s):  
Wei Zhang ◽  
Xiaoming Zhang ◽  
Hui Wang ◽  
Anil K. Sharma ◽  
Albert O. Edwards ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Expression System ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Xenopus Laevis Oocyte ◽  
Cation Selectivity ◽  
Negative Effect ◽  
Dominant Disease ◽  
Vitreoretinal Degeneration ◽  
Inwardly Rectifying

KCNJ13 encodes Kir7.1, an inwardly rectifying K+ channel that is expressed in multiple ion-transporting epithelia. A mutation in KCNJ13 resulting in an arginine-to-tryptophan change at residue 162 (R162W) of Kir7.1 was associated with snowflake vitreoretinal degeneration, an inherited autosomal-dominant disease characterized by vitreous degeneration and mild retinal degeneration. We used the Xenopus laevis oocyte expression system to assess the functional properties of the R162W (mutant) Kir7.1 channel and determine how wild-type (WT) Kir7.1 is affected by the presence of the mutant subunit. Recordings obtained via the two-electrode voltage-clamp technique revealed that injection of oocytes with mutant Kir7.1 cRNA resulted in currents and cation selectivity that were indistinguishable from those in water-injected oocytes, suggesting that the mutant protein does not form functional channels in the plasma membrane. Coinjection of oocytes with equal amounts of mutant and WT Kir7.1 cRNAs resulted in inward K+ and Rb+ currents with amplitudes that were ∼17% of those in oocytes injected with WT Kir7.1 cRNA alone, demonstrating a dominant-negative effect of the mutant subunit. Similar to oocytes injected with WT Kir7.1 cRNA alone, coinjected oocytes exhibited inwardly rectifying Rb+ currents that were more than seven times larger than K+ currents, indicating that mutant subunits did not alter Kir7.1 channel selectivity. Immunostaining of Xenopus oocytes or Madin-Darby canine kidney cells expressing mutant or WT Kir7.1 demonstrated distribution of both proteins primarily in the plasma membrane. Our data suggest that the R162W mutation suppresses Kir7.1 channel activity, possibly by negatively impacting gating by membrane phosphadidylinositol 4,5-bisphosphate.

Evolutionary origins of eukaryotic sodium/proton exchangers

2005 ◽  
Vol 288 (2) ◽  
pp. C223-C239 ◽  
Author(s):  
Christopher L. Brett ◽  
Mark Donowitz ◽  
Rajini Rao
Keyword(s):  
Plasma Membrane ◽  
Drug Sensitivity ◽  
Phylogenetic Analyses ◽  
Subcellular Location ◽  
Monovalent Cation ◽  
Model Organisms ◽  
Sequence Length ◽  
Animal Cells ◽  
Cation Selectivity ◽  
Evolutionary Origins

More than 200 genes annotated as Na+/H+hydrogen exchangers (NHEs) currently reside in bioinformation databases such as GenBank and Pfam. We performed detailed phylogenetic analyses of these NHEs in an effort to better understand their specific functions and physiological roles. This analysis initially required examining the entire monovalent cation proton antiporter (CPA) superfamily that includes the CPA1, CPA2, and NaT-DC families of transporters, each of which has a unique set of bacterial ancestors. We have concluded that there are nine human NHE (or SLC9A) paralogs as well as two previously unknown human CPA2 genes, which we have named HsNHA1 and HsNHA2. The eukaryotic NHE family is composed of five phylogenetically distinct clades that differ in subcellular location, drug sensitivity, cation selectivity, and sequence length. The major subgroups are plasma membrane (recycling and resident) and intracellular (endosomal/TGN, NHE8-like, and plant vacuolar). HsNHE1, the first cloned eukaryotic NHE gene, belongs to the resident plasma membrane clade. The latter is the most recent to emerge, being found exclusively in vertebrates. In contrast, the intracellular clades are ubiquitously distributed and are likely precursors to the plasma membrane NHE. Yeast endosomal ScNHX1 was the first intracellular NHE to be described and is closely related to HsNHE6, HsNHE7, and HsNHE9 in humans. Our results link the appearance of NHE on the plasma membrane of animal cells to the use of the Na+/K+-ATPase to generate the membrane potential. These novel observations have allowed us to use comparative biology to predict physiological roles for the nine human NHE paralogs and to propose appropriate model organisms in which to study the unique properties of each NHE subclass.

scholarly journals Cation channel conductance and pH gating of the innate immunity factor APOL1 are governed by pore-lining residues within the C-terminal domain

2020 ◽  
Vol 295 (38) ◽  
pp. 13138-13149 ◽  
Author(s):  
Charles Schaub ◽  
Joseph Verdi ◽  
Penny Lee ◽  
Nada Terra ◽  
Gina Limon ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Plasma Membrane ◽  
Lipid Bilayers ◽  
Cation Channel ◽  
Planar Lipid Bilayers ◽  
Channel Formation ◽  
Cation Selectivity ◽  
Terminal Domain ◽  
Immunity Factor ◽  
Pore Lining

The human innate immunity factor apolipoprotein L-I (APOL1) protects against infection by several protozoan parasites, including Trypanosoma brucei brucei. Endocytosis and acidification of high-density lipoprotein–associated APOL1 in trypanosome endosomes leads to eventual lysis of the parasite due to increased plasma membrane cation permeability, followed by colloid-osmotic swelling. It was previously shown that recombinant APOL1 inserts into planar lipid bilayers at acidic pH to form pH-gated nonselective cation channels that are opened upon pH neutralization. This corresponds to the pH changes encountered during endocytic recycling, suggesting APOL1 forms a cytotoxic cation channel in the parasite plasma membrane. Currently, the mechanism and domains required for channel formation have yet to be elucidated, although a predicted helix-loop-helix (H-L-H) was suggested to form pores by virtue of its similarity to bacterial pore-forming colicins. Here, we compare recombinant human and baboon APOL1 orthologs, along with interspecies chimeras and individual amino acid substitutions, to identify regions required for channel formation and pH gating in planar lipid bilayers. We found that whereas neutralization of glutamates within the H-L-H may be important for pH-dependent channel formation, there was no evidence of H-L-H involvement in either pH gating or ion selectivity. In contrast, we found two residues in the C-terminal domain, tyrosine 351 and glutamate 355, that influence pH gating properties, as well as a single residue, aspartate 348, that determines both cation selectivity and pH gating. These data point to the predicted transmembrane region closest to the APOL1 C terminus as the pore-lining segment of this novel channel-forming protein.

Effect of salt stress on plasma membrane permeability and lipid saturation in the salt-tolerant yeast Zygosaccharomyces rouxii

1995 ◽  
Vol 80 (2) ◽  
pp. 131-135 ◽  
Author(s):  
Shigetoshi Yoshikawa ◽  
Nobuo Mitsui ◽  
Ken-Ichi Chikara ◽  
Hajime Hashimoto ◽  
Makoto Shimosaka ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Salt Stress ◽  
Membrane Permeability ◽  
Salt Tolerant ◽  
Plasma Membrane Permeability ◽  
Zygosaccharomyces Rouxii

The osmotolerant fructophilic yeast Zygosaccharomyces rouxii employs two plasma-membrane fructose uptake systems belonging to a new family of yeast sugar transporters

Microbiology ◽  
2011 ◽  
Vol 157 (2) ◽  
pp. 601-608 ◽  
Author(s):  
Maria José Leandro ◽  
Hana Sychrová ◽  
Catarina Prista ◽  
Maria C. Loureiro-Dias
Keyword(s):  
Plasma Membrane ◽  
Diffusion Mechanism ◽  
Sugar Transport ◽  
High Capacity ◽  
Transport Systems ◽  
Facilitated Diffusion ◽  
Sugar Transporters ◽  
Zygosaccharomyces Rouxii ◽  
New Family ◽  
Spoilage Yeasts

Owing to its high resistance to weak-acid preservatives and extreme osmotolerance, Zygosaccharomyces rouxii is one of the main spoilage yeasts of sweet foods and beverages. In contrast with Saccharomyces cerevisiae, Z. rouxii is a fructophilic yeast; it consumes fructose faster than glucose. So far, to our knowledge, no specific Z. rouxii proteins responsible for this fructophilic behaviour have been characterized. We have identified two genes encoding putative fructose transporters in the Z. rouxii CBS 732 genome. Heterologous expression of these two Z. rouxii ORFs in a S. cerevisiae strain lacking its own hexose transporters (hxt-null) and subsequent kinetic analysis of sugar transport showed that both proteins are functionally expressed at the plasma membrane: ZrFfz1 is a high-capacity fructose-specific facilitator (K m∼400 mM and V max∼13 mmol h−1 g−1) and ZrFfz2 is a facilitator transporting glucose and fructose with similar capacity and affinity (K m∼200 mM and V max∼4 mmol h−1 g−1). These two proteins together with the Zygosaccharomyces bailii Ffz1 fructose-specific transporter belong to a new family of sugar transport systems mediating the uptake of hexoses via the facilitated diffusion mechanism, and are more homologous to drug/H+ antiporters (regarding their primary protein structure) than to other yeast sugar transporters of the Sugar Porter family.

Sign in / Sign up

Export Citation Format

Share Document