No effect of cAMP on protein synthesis in reticulocyte lysates.

N Grankowski,G Kramer,B Hardesty

doi:10.1016/s0021-9258(18)50732-8

Abstract

The results of a series of experiments are interpreted to indicate that protein synthesis in reticulocyte lysates is not affected by the reticulocyte cAMP-dependent protein kinase. The catalytic subunit of this enzyme was isolated to apparent homogeneity. Also, the protein inhibitor of this protein kinase was isolated from muscle. Neither physiological concentrations of cAMP nor any of these protein components had a detectable effect on protein synthesis in reticulocyte lysates in the presence or absence of exogenous heme. Phosphorylation of the smallest subunit of eukaryotic initiation factor 2 or the 90,000 to 100,000-dalton peptide associated with eukaryotic initiation factor 2 kinase activity were not affected by the activity of the cAMP-dependent protein kinase under conditions in which exogenous heme has a pronounced effect on these reactions.

Highlights

The results of a series of experiments are interpreted to indicate that protein synthesis in reticulocyte lysates is not affected by the reticulocyte
Protein synthesis in rabbit reticulocytes and their cell-free lysates is controlled by the availability of hemin [1, 2]
We report that CAMP, a homogeneous preparation of the catalytic subunit of CAMP-dependent protein kinase isolated from reticulocyt,es, or the inhibitor of this kinase [10] has no detectable effect on protein synthesis in reticulocyte lysates

Summary

No Effect of CAMP on Protein Synthesis in Reticulocyte Lysates*

Gross and Rabinovitz [3] isolated an inhibitor of polypeptide chain initiation from reticulocyte postribosomal supernatant incubated in the absence of hemin This inhibitor, called the hemin-controlled repressor, was formed from an inactive proinhibitor of similar molecular weight. Ochoa and his co-workers [8] concluded that a CAMP-dependent protein kinase or its catalytic subunit can promote the conversion from the inactive proinhibitor to active HCR. Koschel [9] found no effect on protein synthesis in intact cells when intracellular CAMP was raised to very high levels following exposure to catecholamines In this communication, we report that CAMP, a homogeneous preparation of the catalytic subunit of CAMP-dependent protein kinase isolated from reticulocyt,es, or the inhibitor of this kinase [10] has no detectable effect on protein synthesis in reticulocyte lysates

PROCEDURES

RESULTS AND DISCUSSION

CAMP and Protein Synthesis

PROTEIN ADDED