PerspectivePlant biology

How Plant Lysin Motif Receptors Get Activated: Lessons Learned from Structural Biology

Sci. Signal.  26 Jun 2012:
Vol. 5, Issue 230, pp. pe28
DOI: 10.1126/scisignal.2003274

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Abstract

Lysin motif (LysM) receptor kinases are unique to plants and serve important functions in plant-microbe interactions. These proteins recognize microbe-derived N-acetylglucosamine (NAG)–containing ligands, but the molecular mode of ligand perception and of receptor activation has remained unknown. The three-dimensional structure of the LysM receptor kinase CERK1 (chitin elicitor receptor kinase 1) from Arabidopsis thaliana has been reported. CERK1 binds NAG oligomers derived from chitin—the major constituent of fungal cell walls—and mediates immunity to fungal infection. The crystal structure of CERK1 complexed with a NAG pentamer revealed that three NAG moieties attach tightly to one of three lysin motifs within the CERK1 ectodomain. Receptor activation and immune signaling requires, however, ligand-induced CERK1 homodimerization. By acting as bivalent ligands, NAG octamers stabilize CERK1 dimers, providing a structural explanation for why the immunogenic activity of NAG oligomers is restricted to fragments larger than those required for receptor binding. Because CERK1 might serve as a paradigm for the functionality of a whole class of plant LysM proteins, insight into its mode of action will direct future research on these receptors.

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