Phosphorylation of hepatic ribosomal protein S6 on 80 and 40 S ribosomes. Primary structure of S6 in the region of the major phosphorylation sites for cAMP-dependent protein kinases.

摘要: Rat liver ribosomes and 40 S ribosomal subunits were phosphorylated with the purified catalytic subunit of cAMP-dependent protein kinase. Phosphorylation S6 plateaued at around 2 mol phosphate/mol both substrates. Peptide map analyses showed that most prominent phosphorylation sites associated substrates adjacent serines in Arg-Leu-Ser-Ser-Leu-Arg segment S6. The first serine residue appeared to be preferred site as has been established previously for 80 (Wettenhall, R.E.H., Cohen, P. (1982) FEBS Lett. 140, 263-269). Additional apparent from peptide maps. One these was triphosphopeptide (termed T1a) having sequence Arg-Leu-Ser-Ser-Leu-Arg-Ala-Ser-Thr-Ser-Lys. A larger fragment Tlc) isolated mild tryptic digests whole ribosomes, consisted T1a extended by Ser-Glu-Glu-Ser-Gln-(Lys) COOH terminus. comparison size chromatographic isoelectric focusing properties T1a/T1c peptides insulin-stimulated hepatocytes indicated a relationship between peptides. Thus, it some potential region are an insulin-regulated kinase hepatocytes.