Article describing a novel S6 kinase isolated from human placenta which autoactivates through autophosphorylation in vitro. The data supports the hypothesis that this previously uncharacterized S6 kinase belongs to a unique family of protein kinases which utilize autophosphorylation as part of their in vivo activation mechanism.

Article proposing a model in which phosphorylation of sites 1 and 2 occurs sequentially. The model proposes that trypsin treatment of the inactive holoenzyme removes an inhibitory rac-binding domain which blocks MgATP access to the catalytic site. The pseudosubstrate domain at site 1 is autophosphorylated and subsequent bimolecular autophosphorylation at site 2 fully opens the catalytic site.