Subcellular localization and functions of the barley stem rust resistance receptor-like serine/threonine-specific protein kinase Rpg1

Jayaveeramuthu Nirmala, Robert Brueggeman, Christina Maier, Christine Clay, Nils Rostoks, C. Gamini Kannangara, Diter Von Wettstein, Brian J. Steffenson, Andris Kleinhofs

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

The Rpg1 gene confers resistance to many pathotypes of the stem rust fungus Puccinia graminis f. sp. tritici and has protected barley from serious disease losses for over 60 years. Rpg1 encodes a constitutively expressed protein with two tandem kinase domains. Fractionation by differential centrifugation and aqueous two-phase separation of the microsome proteins located Rpg1 mainly in the cytosol but also in the plasma membrane and intracellular membranes. Recombinant Rpg1 autophosphorylates in vitro intramolecularly only serine and threonine amino acids with a preference for Mn2+ cations and a K m of 0.15 and a Vmax of 0.47 nmol·min -1,mg-1 protein. The inability of wild-type Rpg1 to transphosphorylate a recombinant Rpg1 inactivated by site-directed mutation confirmed that Rpg1 autophosphorylation proceeds exclusively via an intramolecular mechanism. Site-directed mutagenesis of the two adjacent lysine residues in the ATP anchor of the two-kinase domains established that the first of the two tandem kinase domains is nonfunctional and that lysine 461 of the second domain is the catalytically active residue. Transgenic barley, expressing Rpg1 mutated in either the kinase 1 or 2 domains, were fully susceptible to P. graminis f. sp. tritici revealing requirement of both kinase domains for resistance. In planto-expressed Rpg1 mutant protein confirmed that mutation in domain 2, but not 1, rendered the protein incapable of autophosphorylation.

Original languageEnglish (US)
Pages (from-to)7518-7523
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume103
Issue number19
DOIs
StatePublished - May 9 2006

Keywords

  • Cultivar
  • Protein kinase 1 domain
  • Protein kinase 2 domain

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