Energetic and Molecular Water Permeation Mechanisms of the Human Red Blood Cell Urea Transporter B

Energetic and Molecular Water Permeation Mechanisms of the Human Red Blood Cell Urea Transporter B

Urea transporter B (UT-B) is a passive membrane channel that facilitates highly efficient permeation of urea. In red blood cells (RBC), while the major function of UT-B is to transport urea, it is assumed that this protein is able to conduct water. Here, we have revisited this last issue by studying RBCs and ghosts from human variants with defects of aquaporin 1 (AQP1) or UT-B. We found that UT...

Water and urea permeation pathways of the human excitatory amino acid transporter EAAT1.

Glutamate transport is coupled to the co-transport of 3 Na(+) and 1 H(+) followed by the counter-transport of 1 K(+). In addition, glutamate and Na(+) binding to glutamate transporters generates an uncoupled anion conductance. The human glial glutamate transporter EAAT1 (excitatory amino acid transporter 1) also allows significant passive and active water transport, which suggests that water pe...

Structure and permeation mechanism of a mammalian urea transporter.

As an adaptation to infrequent access to water, terrestrial mammals produce urine that is hyperosmotic to plasma. To prevent osmotic diuresis by the large quantity of urea generated by protein catabolism, the kidney epithelia contain facilitative urea transporters (UTs) that allow rapid equilibration between the urinary space and the hyperosmotic interstitium. Here we report the first X-ray cry...

Molecular Mechanisms of Plasmodium Red Blood Cell Invasion

Upregulation of urea transporter UT-A2 and water channels AQP2 and AQP3 in mice lacking urea transporter UT-B.

The UT-B urea transporter is the major urea transporter in red blood cells and kidney descending vasa recta. Humans and mice that lack UT-B have a mild urine-concentrating defect. Whether deletion of UT-B altered the expression of other transporter proteins involved in urinary concentration was tested. Fluorescence-based real-time reverse transcription-PCR and Northern blot analysis showed upre...