Mosaicism in Vacuolating Cytotoxin Alleles of Helicobacter pylori

Abstract

The Arabidopsis hyperpolarization-activated (inward-rectifying) K+ channel KAT1 is structurally more similar to animal depolarization-activated (outward-rectifying) K+ channels than to animal hyperpolarization-activated K+ channels. To gain insight into the structural basis for the opposite voltage dependences of plant inward-rectifying and animal outward-rectifying K+ channels, we constructed recombinant chimeric channels between the hyperpolarization-activated K+ channel KAT1 and a Xenopus depolarization-activated K+ channel. We report here that two of the chimeric constructs, which contain the first third of the KAT1 sequence, including the first four membrane-spanning segments (S1-S4) and the linker sequence between the fourth and fifth membrane-spanning segments, express functional channels that retain activation by hyperpolarization, but not depolarization. These two chimeric channels are no longer selective for K+. The chimeras are selective for cations over anions and are permeable to Ca2+. Therefore, unlike animal hyperpolarization-activated K+ channels, in which the carboxyl terminus is important for inward rectification induced by Mg2+ and polyamine block, the plant KAT1 channel has its major determinants for inward rectification in the amino-terminal region, which ends at the end of the S4-S5 linker.

Role of Helicobacter pylori infection in cancer‐associated fibroblast‐induced epithelial‐mesenchymal transition in vitro

“…The H. pylori strain negative for CagA and VacA ( H. pylori cagA−vacA− (s2/m2) 42 originated from our bacterial bank of isolations from gastric biopsy specimens of the patients with gastric ulcer who underwent upper endoscopy. The genomic DNA was isolated from H. pylori strains using Genomic mini (A&A Biotechnology, Gdynia, Poland).…”

Analysis of geospecific markers for Helicobacter pylori variants in patients from Japan and Nigeria by triple-locus nucleotide sequence typing

“…Vacuolating cytotoxin (vacA) genotyping based on signal and mid-region alleles was performed as previously described (Atherton et al, 1999;Owen et al, 2002).…”

Genotipificación de los factores de virulencia vacA y cagA de Helicobacter pylori en individuos de dos regiones de Colombia con riesgo opuesto de cáncer gástrico

“…Este gen contiene dos regiones variables: la región s, que codifica el péptido señal y presenta dos variantes alélicas, s1 y s2, y la región m, o región media, que presenta las variantes alélicas m1 y m2. Los aislamientos de H. pylori con las combinaciones s1m1 y s1m2 producen, respectivamente, niveles altos y moderados de citotoxina, mientras que los aislamientos con la combinación s2m2 producen muy poca citotoxina o no la producen (14).…”