title: Unexpected structure of the Ca2+-regulatory region from soybean calcium-dependent protein kinase-alpha.
abstract: Calcium-dependent protein kinases (CDPKs) are an extensive class of multidomain Ca(2+)-regulated enzymes from plants and protozoa. In vivo the so-called calmodulin-like domain (CLD) of CDPK binds intramolecularly to the junction domain (JD), which exhibits both kinase-inhibitory and CLD binding properties. Here we report the high resolution solution structure of the calcium-regulatory region from soybean CDPK-alpha determined in the presence of a peptide encompassing the JD. The structure of both lobes of CLD resembles that of related helix-loop-helix Ca(2+)-binding proteins. NMR chemical shift mapping studies demonstrate that the JD induces significant structural changes in isolated Ca(2+)-CLD, particularly the C-terminal domain, although a stable complex is not formed. A CLD solution structure calculated on the basis of NMR data and long range fluorescence resonance energy transfer distances reveals an activated state with both lobes positioned side by side, similar to calcineurin B rather than calmodulin, highlighting the possible pitfall of assigning function purely from sequence information.
authors.affiliation: Structural Biology Research Group, Department of Biological Sciences, University of Calgary, 2500 University Dr. N. W., Calgary, Alberta T2N 1N4, Canada.
authors.forename: Aalim M
authors.initials: AM
authors.lastname: Weljie
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Vogel
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D004789:Enzyme Activation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D013025:Glycine max / Q000737:chemistry / Q000201:enzymology*; D013379:Substrate Specificity; D017871:Calcium-Calmodulin-Dependent Protein Kinases
chemical_list: D002118:Calcium; D002135:Calcium-Binding Proteins; D010940:Plant Proteins; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases