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Publication Abstract from PubMed

The perception of two plant germination inducers, karrikins and strigolactones, are mediated by the proteins KAI2 and D14. Recently, KAI2-type proteins from parasitic weeds, which are possibly related to seed germination induced by strigolactone, have been classified into three clades characterized by different responses to karrikin/strigolactone. Here we characterized a karrikin-binding protein in Striga (ShKAI2iB) that belongs to intermediate-evolving KAI2 and provided the structural bases for its karrikin-binding specificity. Binding assays showed that ShKAI2iB bound karrikins but not strigolactone, differing from other KAI2 and D14. The crystal structures of ShKAI2iB and ShKAI2iB-karrikin complex revealed obvious structural differences in a helix located at the entry of its ligand-binding cavity. This results in a smaller closed pocket, which is also the major cause of ShKAI2iB's specificity of binding karrikin. Our structural study also revealed that a few non-conserved amino acids led to the distinct ligand-binding profile of ShKAI2iB, suggesting that the evolution of KAI2 resulted in its diverse functions.

Structural basis of unique ligand specificity of KAI2-like protein from parasitic weed Striga hermonthica.,Xu Y, Miyakawa T, Nakamura H, Nakamura A, Imamura Y, Asami T, Tanokura M Sci Rep. 2016 Aug 10;6:31386. doi: 10.1038/srep31386. PMID:27507097^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.