Protein-chitin interactions in the arthropod cuticle

The cuticle of insects and other arthropods is a composite material composed of microfibrils of the polysaccharide chitin embedded in a matrix of cuticular proteins. One group of proteins found in the cuticle is frequently designated as the CPR class, due to the presence of a conserved domain known as the R&R consensus. Several groups have shown that this domain acts as a chitin-binding domain. We have produced a fusion protein with glutathione-S-transferase fused to the R&R consensus from an Anopheles gambiae cuticular protein, and measured chitin binding using fusion protein isolated using either sonication or chemical lysis. We have also measured the affinity of the chitin-protein interaction using isothermal titration calorimetry. We have constructed a structural model for the R&R consensus using homology modeling and docked a chitin fragment to our model in order to identify residues that may be critical in chitin binding.