title: TOUSLED is a nuclear serine/threonine protein kinase that requires a coiled-coil region for oligomerization and catalytic activity.
abstract: The TOUSLED (TSL) gene is essential for the proper morphogenesis of leaves and flowers in Arabidopsis thaliana. Protein sequence analysis predicts TSL is composed of a carboxyl-terminal protein kinase catalytic domain and a large amino-terminal regulatory domain. TSL fusion proteins, expressed in and purified from yeast, were used to demonstrate TSL protein kinase activity in vitro. TSL trans-autophosphorylates on serine and threonine residues, and phosphorylates exogenous substrates. Using the yeast two-hybrid system, TSL was found to oligomerize via its NH2-terminal domain. A deletion series indicates that a region containing two alpha-helical segments predicted to participate in a coiled-coil structure is essential for oligomerization. TSL localizes to the nucleus in plant cells through an essential NH2-terminal nuclear localization signal; however, this signal is not necessary for protein kinase activity. Finally, deletion mutants demonstrate a strict correlation between catalytic activity and the ability to oligomerize, arguing that activation of the protein kinase requires interaction between TSL molecules.
authors.affiliation: Department of Plant Biology, University of California, Berkeley, California 94720, USA. jlr@nature.berkeley.edu
authors.forename: J L
authors.initials: JL
authors.lastname: Roe
authors.forename: T
authors.initials: T
authors.lastname: Durfee
authors.forename: J R
authors.initials: JR
authors.lastname: Zupan
authors.forename: P P
authors.initials: PP
authors.lastname: Repetti
authors.forename: B G
authors.initials: BG
authors.lastname: McLean
authors.forename: P C
authors.initials: PC
authors.lastname: Zambryski
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins; D015153:Blotting, Western; D016350:Leucine Zippers; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D017384:Sequence Deletion
chemical_list: D029681:Arabidopsis Proteins; D011494:Protein Kinases; C084661:tousled protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases