RS repeat peptide is a serine/arginine-rich peptide substrate for CDC-like kinase 1 (Clk1).[1],[2] It has been used to identify inhibitors of Clk1 with anticancer activity.
References:
[1].Araki, S., Dairiki, R., Nakayama, Y., et al.Inhibitors of CLK protein kinases suppress cell growth and induce apoptosis by modulating pre-mRNA splicingPLoS One10(1)e0116929(2015).
[2].Schmitt, C., Kail, D., Mariano, M., et al.Design and synthesis of a library of lead-like 2,4-bisheterocyclic substituted thiophenes as selective Dyrk/Clk inhibitorsPLoS One9(3)e87851(2014).