The three cloned Stb genes, which are effective against different pathogen isolates, encode diverse receptor-like kinases with extracellular domains potentially involved in sugar binding.
Like other RTKs, ERBB receptors can exist ... Ullrich, A. The discovery of receptor tyrosine kinases: Targets for cancer therapy. Nature Reviews Cancer 4, 361–370 (2004) doi:10.1038/nrc1360.
The first is a novel family of enzymes called the G protein–coupled receptor kinases (GRKs) including the βadrenergic receptor kinase (βRK), and the second is a group of proteins called arrestins.