This peptide is a pseudosubstrate for a number of serine/threonine kinases, including protein kinase A (PKA), protein kinase B (PKB), protein kinase C (PKC), protein kinase CHK1, and glycogen synthase kinase 3 (GSK3) different isoforms. The peptide sequence is derived from the residues 19-31 of human protein kinase C isoforms alpha and beta, which contains the R-X-X-S/T consensus motif for Ser/Thr kinases that phosphorylate the Ser25 within this peptide. Arg-Phe-Ala-Arg-Lys-Gly-Ser-Leu-Arg-Gln-Lys-Asn-Val or RFARKGSLRQKNV