Detection and investigation of a protein factor concerned with the stimulation of disulfide reductase activity by cyclic AMP and other effectors

Abstract

Stimulation of disulfide reductase (DSR) in the supernatant fraction of mouse liver by 3′,5′-AMP (10−7 M), ATP (5·10−5 M), Mg++ (5·10−5 M), EDTA (5·10−4 M), and protamine (5 mg/ml) is mediated by a factor which is readily adsorbed by BaSO4, Al(OH)3, and activated charcoal, and is readily eluted by a tenfold increase in the molarity of the buffer. Barium eluates of the liver and brain mutually and equally restore the effect of 3′,5′-AMP when abolished by BaSO4. The adsorbed factor is evidently a protein, for it does not dialyze, it is very thermolabile, and it is easily inactivated by low concentrations of trypsin. The factor restores activation of DSR when abolished or reduced by protein inhibitor of protein kinase (PIPK). The fact that the relationship between the active quantities of PIPK and protein factor (PF) is linear indicates that the PF is similar or identical to protein kinase. The possible biological role of activation of DSR and the hypothesis that a special protamine-sensitive protein kinase exists are discussed.