Note on the activation of the heme-stabilized translational inhibitor of reticulocyte lysates by oxidized glutathione.

The heme-controlled translational inhibitor (HCI) of reticulocyte lysates can be activated either by a lack of by heme or, in the presence of heme, by oxidized glutathione (GSSG) and various oxidative processes. The latter activation can be prevented or reversed by NADPH or NADPH generators, such as glucose-6-phosphate (G-6-P). Since reticulocyte lysates contain a very active GSSG reductase, it was conceivable that GSSG acts by draining lysate NADPH via the reaction GSSG + NADPH + H+ in equilibrium 2 GSH + NADP+. However, removal of lysate GSSG reductase by its corresponding antibody has no effect on the activity of GSSG. This supports previous observations with lysates depleted of GSSG reductase by affinity chromatography and supports the notion that GSSG activates HCI in a more direct fashion. The role of NADPH generation in maintaining HCI in its inactive, pro-HCI form is further supported by the observation that the addition of anti-lysate G-6-P dehydrogenase antibody leads to activation of HCI in reticulocyte lysates.