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Single-channel water permeabilities of Escherichia coli aquaporins AqpZ and GlpF.

ABSTRACT: From equilibrium molecular dynamics simulations we have determined single-channel water permeabilities for Escherichia coli aquaporin Z (AqpZ) and aquaglyceroporin GlpF with the channels embedded in lipid bilayers. GlpF's osmotic water permeability constant pf exceeds by 2-3 times that of AqpZ and the diffusive permeability constant (pd) of GlpF is found to exceed that of AqpZ 2-9-fold. Achieving complete water selectivity in AqpZ consequently implies lower transport rates overall relative to the less selective, wider channel of GlpF. For AqpZ, the ratio pf/pd congruent with 12 is close to the average number of water molecules in the channel lumen, whereas for GlpF, pf/pd congruent with 4. This implies that single-file structure of the luminal water is more pronounced for AqpZ, the narrower channel of the two. Electrostatics profiles across the pore lumens reveal that AqpZ significantly reinforces water-channel interactions, and weaker water-water interactions in turn suppress water-water correlations relative to GlpF. Consequently, suppressed water-water correlations across the narrow selectivity filter become a key structural determinant for water permeation causing luminal water to permeate slower across AqpZ.

SUBMITTER: Jensen MO

PROVIDER: S-EPMC1403167 | biostudies-literature | 2006 Apr

REPOSITORIES: biostudies-literature

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Single-channel water permeabilities of Escherichia coli aquaporins AqpZ and GlpF.

Jensen Morten Ø MØ Mouritsen Ole G OG

Biophysical journal 20060106 7

From equilibrium molecular dynamics simulations we have determined single-channel water permeabilities for Escherichia coli aquaporin Z (AqpZ) and aquaglyceroporin GlpF with the channels embedded in lipid bilayers. GlpF's osmotic water permeability constant pf exceeds by 2-3 times that of AqpZ and the diffusive permeability constant (pd) of GlpF is found to exceed that of AqpZ 2-9-fold. Achieving complete water selectivity in AqpZ consequently implies lower transport rates overall relative to th ...[more]

PMID: 16399837

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Project description:The study was to determine whether the expression of genes involved in intestinal water and ion transport would be affected by enterotoxigenic (ETEC) K88 both in vitro and in vivo. First, 36 male piglets (4 d old) were randomly allotted to either the control or the ETEC K88 group. Each group had 6 replicates with 3 piglets per replicate. All piglets were fed with the same diets for 17 d. On d 15, piglets in the ETEC K88 group were challenged with ETEC K88 (serotype O149:K91:K88ac) at 1 × 10 cfu per pig, whereas those in the control group received the same volume of sterile PBS. After being challenged with ETEC K88 for 72 h (d 18), 1 piglet from each replicate was selected for slaughter to collect samples from the jejunum, ileum, and colon. The mRNA expression and protein abundance of cystic fibrosis transmembrane conductance regulator (CFTR) in the ileum and colon were increased compared with that in the control group ( < 0.05). Furthermore, the mRNA expression of () in the ileum and colon was increased by ETEC K88 challenge ( < 0.05), whereas in the jejunum, both its mRNA and protein expression were increased by ETEC K88 treatment ( < 0.05). Additionally, an established porcine intestinal epithelial cell line (IPEC-J2) was used to investigate the effect and possible mechanism of ETEC K88 on expression of water channel aquaporins (AQP) and ion transporters. Cells (1.17 × 10 per well) were grown in 6-well plates and treated with ETEC K88 at a multiplicity of infection of 50:1 for 3 h. The mRNA expression of , , and () in IPEC-J2 cells was reduced after ETEC K88 treatment ( < 0.05). Further analyses using western blotting also demonstrated that ETEC K88 decreased the protein expression of AQP3, AQP9, and AQP11 in IPEC-J2 cells ( < 0.05). Moreover, the phosphorylation levels of protein kinase A (PKA) and cyclic adenosine monophosphate (cAMP)-response element binding protein (CREB) were decreased by ETEC K88 challenge ( < 0.05). The results indicate that ETEC K88 challenge induced differential expression of intestinal ion transporters and AQP in young piglets, probably by regulation of the cAMP-PKA signaling pathway. This study might provide new insights about the importance of fluid homeostasis in control of ETEC-induced diarrhea in young piglets.

Dataset Information

Single-channel water permeabilities of Escherichia coli aquaporins AqpZ and GlpF.

Publications

Single-channel water permeabilities of Escherichia coli aquaporins AqpZ and GlpF.

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