S6 kinase substrate

This sequence, AKRRRLSSLRA, derived from rat hepatic 40S ribosomal protein S6 (229-239). Substrate for Rho-kinase II (ROCK II), Km=0,9 µM and for p90 rsk (S6K) in cell extracts (Km=0,18 mM) using phosphocellulose assay. Peptide phosphorylation by PKS and PKC can be eliminated by the inclusion of PKI and EGTA, respectively, in the assay.