Structural characterization of the RLCK family member BSK8: A pseudokinase with an unprecedented architecture

Christian Grütter, Shivakumar Sreeramulu, Guido Sessa, Daniel Rauh*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Brassinosteroid signaling kinases (BSKs) are plant-specific receptor-like cytoplasmic protein kinases involved in the brassinosteroid signaling pathway. Unlike common protein kinases, they possess a naturally occurring alanine residue at the "gatekeeper" position, as well as other sequence variations. How BSKs activate downstream proteins such as BSU1, as well as the structural consequences of their unusual sequential features, was unclear. We crystallized the catalytic domain of BSK8 and solved its structure by multiple-wavelength anomalous dispersion phasing methods to a resolution of 1.5 Å. In addition, a co-crystal structure of BSK8 with 5-adenylyl imidodiphosphate (AMP-PNP) revealed unusual conformational arrangements of the nucleotide phosphate groups and catalytic key motifs, typically not observed for active protein kinases. Sequential analysis and comparisons with known pseudokinase structures suggest that BSKs represent constitutively inactive protein kinases that regulate brassinosteroid signal transfer through an allosteric mechanism.

Original languageEnglish
Pages (from-to)4455-4467
Number of pages13
JournalJournal of Molecular Biology
Issue number22
StatePublished - 15 Nov 2013


FundersFunder number
German National Genome Research Network-Plus
United States-Israel Binational Science FoundationBSF 2007091
Bundesministerium für Bildung und Forschung01GS08104


    • BR signaling kinase (BSK)
    • X-ray crystallography
    • brassinosteroid (BR) signaling
    • pseudokinase
    • receptor-like protein kinases


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