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Aquaporin 0-calmodulin interaction and the effect of aquaporin 0 phosphorylation.

Rose KM, Wang Z, Magrath GN, Hazard ES, Hildebrandt JD, Schey KL
Biochemistry. 2008 47 (1): 339-47

PMID: 18081321 · DOI:10.1021/bi701980t

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 S231 and S235, 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.

MeSH Terms (15)

Amino Acid Sequence Aquaporins Calmodulin Eye Proteins Membrane Glycoproteins Models, Molecular Molecular Sequence Data Phosphorylation Protein Binding Protein Structure, Secondary Protein Structure, Tertiary Sequence Homology, Amino Acid Spectrometry, Fluorescence Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization Trypsin

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