2o9d
Crystal Structure of AqpZ mutant T183C.
Structural highlights
FunctionAQPZ_ECOLI Channel that permits osmotically driven movement of water in both directions. It is involved in the osmoregulation and in the maintenance of cell turgor during volume expansion in rapidly growing cells. It mediates rapid entry or exit of water in response to abrupt changes in osmolarity.[1] [2] [3] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe aquaporin family of channels was defined based on the inhibition of water transport by mercurial compounds. Despite the important role of mercurials, little is known about the structural changes involved upon mercury binding leading to channel inhibition. To elucidate the mechanism we designed a mutant, T183C, of aquaporin Z (AqpZ) patterned after the known mercury-sensitive site of aquaporin 1 (AQP1) and determined the X-ray crystal structures of the unbound and mercury blocked states. Superposition of the two structures shows no conformational rearrangement upon mercury binding. In the blocked structure, there are two mercury sites, one bound to Cys183 and occluding the pore, and a second, also bound to the same cysteine but found buried in an interstitial cavity. To test the mechanism of blockade we designed a different mutant, L170C, to produce a more effective mercury block at the pore site. In a dose-response inhibition study, this mutant was 20 times more sensitive to mercury than wild-type AqpZ and four times more sensitive than T183C. The X-ray structure of L170C shows four mercury atoms at, or near, the pore site defined in the T183C structure and no structural change upon mercury binding. Thus, we elucidate a steric inhibition mechanism for this important class of channels by mercury. Structural basis of aquaporin inhibition by mercury.,Savage DF, Stroud RM J Mol Biol. 2007 May 4;368(3):607-17. Epub 2007 Mar 2. PMID:17376483[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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