3K3F: Crystal Structure of the Urea Transporter from Desulfovibrio Vulgaris

Citation:
Abstract
Urea is highly concentrated in the mammalian kidney to produce the osmotic gradient necessary for water re-absorption. Free diffusion of urea across cell membranes is slow owing to its high polarity, and specialized urea transporters have evolved to achieve rapid and selective urea permeation. Here we present the 2.3 A structure of a functional urea transporter from the bacterium Desulfovibrio vulgaris. The transporter is a homotrimer, and each subunit contains a continuous membrane-spanning pore formed by the two homologous halves of the protein. The pore contains a constricted selectivity filter that can accommodate several dehydrated urea molecules in single file. Backbone and side-chain oxygen atoms provide continuous coordination of urea as it progresses through the filter, and well-placed alpha-helix dipoles provide further compensation for dehydration energy. These results establish that the urea transporter operates by a channel-like mechanism and reveal the physical and chemical basis of urea selectivity.
PDB ID: 3K3FDownload
MMDB ID: 78218
PDB Deposition Date: 2009/10/2
Updated in MMDB: 2009/12
Experimental Method:
x-ray diffraction
Resolution: 2.3  Å
Source Organism:
Similar Structures:
Biological Unit for 3K3F: trimeric; determined by author and by software (PISA)
Molecular Components in 3K3F
Label Count Molecule
Proteins (3 molecules)
3
Urea Transporter(Gene symbol: DVU1160)
Molecule annotation
Chemicals (27 molecules)
1
27
* Click molecule labels to explore molecular sequence information.

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