1. Aquaporin 0—Calmodulin Interaction and the Effect of Aquaporin 0 Phosphorylation.
- Author
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Lindsey Rose, K. M., Wang, Z., Magrath, G. N., Hazard, E. S., Hildebrandt, J. D., and Schey, K. L.
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AQUAPORINS , *MEMBRANE proteins , *CALMODULIN , *PHOSPHORYLATION , *PEPTIDES - Abstract
Aquaporin 0 (AQP0), also known as major intrinsic protein of lens, is the most abundant membrane protein in the lens and it undergoes a host of C-terminally directed posttranslational modifications. The C-terminal region containing the major phosphorylation sites is a putative calmodulin-binding, site, and calmodulin has been shown to regulate AQP0 water permeability. The purpose of the present study was to elucidate the role of AQP0 phosphorylation on calmodulin binding. AQP0 C-terminal peptides were synthesized with and without serine phosphorylation on $231 and $235, and the ability of these peptides to bind dansyl-labeled calmodulin and the calcium dependence of the interaction was assessed using a fluorescence binding assay. The AQP0 C-terminal phosphorylated peptides were found to have 20-50-fold lower affinities for calmodulin than the unphosphorylated peptide. Chemical cross-linking studies revealed specific sites of AQP0-calmodulin interaction that are significantly reduced by AQP0 phosphorylation. These data suggest that AQP0 C-terminal phosphorylation affects calmodulin binding in vivo and has a role in regulation of AQP0 function. [ABSTRACT FROM AUTHOR]
- Published
- 2008
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