This domain is the binding/interacting region of several protein kinases, such as the Schizosaccharomyces pombe Byr2. Byr2 is a Ser/Thr-specific protein kinase acting as mediator of signals for sexual differentiation in S. pombe by initiating a MAPK module, which is a highly conserved element in eukaryotes. Byr2 is activated by interacting with Ras, which then translocates the molecule to the plasma membrane. Ras proteins are key elements in intracellular signaling and are involved in a variety of vital processes such as DNA transcription, growth control, and differentiation. They function like molecular switches cycling between GTP-bound 'on' and GDP-bound 'off' states [1].

1: The Ras-Byr2RBD complex: structural basis for Ras effector recognition in yeast. Scheffzek K, Grunewald P, Wohlgemuth S, Kabsch W, Tu H, Wigler M, Wittinghofer A, Herrmann C; Structure. 2001;9:1043-1050. PMID:11709168