Rsk2 allosterically activates estrogen receptor alpha by docking to the hormone-binding domain.
Clark DE, Poteet-Smith CE, Smith JA, Lannigan DA, EMBO J, 2001 Jul 2 - link

Identification of an extracellular signal-regulated kinase (ERK) docking site in ribosomal S6 kinase, a sequence critical for activation by ERK in vivo.
Smith JA, Poteet-Smith CE, Malarkey K, Sturgill TW, J Biol Chem, 1999 Jan 29 - link