High pO2-activated inhibitor of protein synthesis in rabbit reticulocytes: its relationship to glutathione disulfide-induced inhibitor and to a approximately 23,000-Mr sulfhydryl protein.

The treatment of reticulocyte post-ribosomal supernatant containing ribosome wash with high pO2 or glutathione disulfide resulted in the activation of an inhibitor of protein synthesis of approximately 23,000-Mr as implicated by its elution from Sephadex G-100. This inhibitor could also be directly activated by exposure of the approximately 23,000-Mr fractions of the control eluate to high pO2 or glutathione disulfide. The high pO2-dependent activation of the inhibitor was blocked by the presence of glucose-6-phosphate or cAMP (2 mM). The inhibitor was stable (and activable) during a 5 minute incubation at 80 degrees C. The analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the G-100 (approximately 23,000-Mr) fractions treated with [14C]N-ethylmaleimide revealed the abolishment of the label in a approximately 23,000-Mr protein band in parallel to high pO2-dependent inhibitor activation.