Polyclonal Antibody to p70 S6 Kinase (Ab-424)

RPS6KB1 phosphorylates the Ribosomal Protein-S6. Activation of RPS6KB1 requires a complex, ordered series of conformational changes and phosphorylation reactions. While the role of sequential, multi-site phosphorylation has been extensively detailed, characterization of the priming step required to initiate this cascade has remained elusive. Probably this priming process is dependent on calcium. Calcium-dependent regulation of RPS6KB1 does not specifically target Thr-229 and Thr-389, the key regulatory phosphorylation sites; rather, calcium chelation results in a global inhibition of RPS6KB1 phosphorylation. The initial calcium-dependent process is required to release an inhibitory interaction between the C- and N-termini of RPS6KB1, thus allowing phosphorylation of key domains. The priming event involves formation of a calcium-dependent protein complex that releases the interaction between the N- and C-termini. RPS6KB1 is then accessible for activation by the kinases that target the known regulatory phosphorylation sites . Satoru Eguchi et al. (1999) J Biol Chem, Vol. 274: 36843-36851 Papst PJ, et al. (1998) J Biol Chem. 273 (24) :15077-84. Ulrike Krause et al. (2002) Eur. J. Biochem. 269: 3751-3759 c Le, X.F, et al. (2003) Oncogene 22: 484