Are there chitin receptors?
A receptor is defined as a molecule (typically a protein, often a transmembrane protein) that specifically and saturably binds a ligand and upon binding triggers some kind of cellular response (typically a signal cascade). Plant cells are known to perceive chitin oligomers by surface receptors in their plasma membranes. These are complex, multi-component protein complexes which upon chitin binding appear to dimerize as a precondition for signal cascade triggering. Similar, but slightly different models have been proposed for chitin perception in the model plant Arabidopsis thaliana (a dicot) and rice (a monocot), but the exact composition of the receptor complexes, the binding mode of chitin oligomers, the mechanism of dimerization and of activating the signal cascade are still under debate. Humans contain a number of enzymatically inactive 'chitinases' which are thought to act as chitin receptors, but their involvement in different responses is not clear.