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PDBsum entry 3riz
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Signaling protein
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PDB id
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3riz
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References listed in PDB file
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Key reference
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Title
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Structural basis of steroid hormone perception by the receptor kinase bri1.
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Authors
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M.Hothorn,
Y.Belkhadir,
M.Dreux,
T.Dabi,
J.P.Noel,
I.A.Wilson,
J.Chory.
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Ref.
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Nature, 2011,
474,
467-471.
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PubMed id
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Abstract
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Polyhydroxylated steroids are regulators of body shape and size in higher
organisms. In metazoans, intracellular receptors recognize these molecules.
Plants, however, perceive steroids at membranes, using the membrane-integral
receptor kinase BRASSINOSTEROID INSENSITIVE 1 (BRI1). Here we report the
structure of the Arabidopsis thaliana BRI1 ligand-binding domain, determined by
X-ray diffraction at 2.5 Å resolution. We find a superhelix of 25 twisted
leucine-rich repeats (LRRs), an architecture that is strikingly different from
the assembly of LRRs in animal Toll-like receptors. A 70-amino-acid island
domain between LRRs 21 and 22 folds back into the interior of the superhelix to
create a surface pocket for binding the plant hormone brassinolide. Known loss-
and gain-of-function mutations map closely to the hormone-binding site. We
propose that steroid binding to BRI1 generates a docking platform for a
co-receptor that is required for receptor activation. Our findings provide
insight into the activation mechanism of this highly expanded family of plant
receptors that have essential roles in hormone, developmental and innate
immunity signalling.
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