4jym
From Proteopedia
crystal Structure of KAI2 in complex with 3-methyl-2H-furo[2,3-c]pyran-2-one
Structural highlights
FunctionKAI2_ARATH Involved in seed germination and seedling development. Essential for plant responses to karrikins, a class of butenolide compounds, structurally similar to strigolactones, released from burning vegetation that stimulate seed germination and enhance seedling photomorphogenesis. KAI2 is not required for strigolactone-mediated responses, but MAX2 is necessary for responses to karrikins and strigolactones.[1] [2] [3] [4] Publication Abstract from PubMedGenetic studies in Arabidopsis implicate an alpha/beta-hydrolase, KARRIKIN-INSENSITIVE 2 (KAI2) as a receptor for karrikins, germination-promoting butenolide small molecules found in the smoke of burned plants. However, direct biochemical evidence for the interaction between KAI2 and karrikin and for the mechanism of downstream signaling by a KAI2-karrikin complex remain elusive. We report crystallographic analyses and ligand-binding experiments for KAI2 recognition of karrikins. The karrikin-1 (KAR1) ligand sits in the opening to the active site abutting a helical domain insert but distal from the canonical catalytic triad (Ser95-His246-Asp217) of alpha/beta-hydrolases, consistent with the lack of detectable hydrolytic activity by purified KAI2. The closest approach of KAR1 to Ser95-His246-Asp217 is 3.8 A from His246. Six aromatic side chains, including His246, encapsulate KAR1 through geometrically defined aromatic-aromatic interactions. KAR1 binding induces a conformational change in KAI2 at the active site entrance. A crevice of hydrophobic residues linking the polar edge of KAR1 and the helical domain insert suggests that KAI2-KAR1 creates a contiguous interface for binding signaling partners in a ligand-dependent manner. Smoke-derived karrikin perception by the alpha/beta-hydrolase KAI2 from Arabidopsis.,Guo Y, Zheng Z, La Clair JJ, Chory J, Noel JP Proc Natl Acad Sci U S A. 2013 Apr 23. PMID:23613584[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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