title: Impact of Ca(2+) on structure of soybean CDPKβ and accessibility of the Tyr-24 autophosphorylation site.
abstract: Several plant CDPKs were recently shown to be dual specificity kinases rather than Ser/Thr kinases as traditionally classified by sequence analysis. In the present study we confirm the autophosphorylation of recombinant soybean His 6-GmCDPKβ at the Tyr-24 site using sequence- and modification- specific antibodies. Homology modeling of soybean CDPKβ based on recent structures determined for several apicomplexan CDPKs suggested that phosphotyrosine-24 may be inaccessible to phosphatases. However, we report that dephosphorylation of CDPKβ by the protein tyrosine phosphatase 1B, PTP1B, was not restricted in the presence of calcium. Thus, despite conformational changes likely associated with calcium binding to the CDPKs, phosphotyrosine sites remain fully accessible to dephosphorylation suggesting the possibility of conformational breathing and flexing.
authors.affiliation: Department of Plant Biology; University of Illinois; Urbana, IL USA; Department of Biological Science; College of Biological Sciences and Biotechnology; Chungnam National University; Daejeon, South Korea.
authors.forename: Man-Ho
authors.initials: MH
authors.lastname: Oh
authors.affiliation: Department of Genome Sciences; University of Washington; Seattle, WA USA.
authors.forename: Xia
authors.initials: X
authors.lastname: Wu
authors.affiliation: Department of Plant Biology; University of Illinois; Urbana, IL USA; US Department of Agriculture; Agricultural Research Service; Urbana, IL USA.
authors.forename: Steven C
authors.initials: SC
authors.lastname: Huber
mesh_terms: D000595:Amino Acid Sequence; D002118:Calcium / Q000494:pharmacology*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism*; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000378:metabolism; D013025:Glycine max / Q000201:enzymology*; D040681:Structural Homology, Protein; D014122:Toxoplasma / Q000201:enzymology
chemical_list: D019000:Phosphotyrosine; D011494:Protein Kinases; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D002118:Calcium
keywords: calcium signaling; conformational change; homology modeling; modification-specific antibodies; protein tyrosine phosphatase 1B (PTP1B); tyrosine autophosphorylation