The aim of this study was to analyze the N-terminal post-translational inco
rporation of arginine into cytosolic proteins from cultured cells and the i
n vitro incorporation of arginine into soluble proteins of PC12 cells after
serum deprivation. Arginine incorporation was measured in the presence of
protein synthesis inhibitors. None of the inhibitors used affected signific
antly the arginylation reaction while the novo synthesis of protein was red
uced by 98%. Under these conditions, we found that of the total [C-14]argin
ine incorporated into the proteins, around 20% to 40% was incorporated into
the N-terminal position of soluble proteins by a post-translational mechan
ism. These results suggest that this post-translational aminoacylation may
be a widespread reaction in neuronal and non-neuronal cells. We also found
that in PC12 cells, the in vitro post-translational arginylation was 60% hi
gher in apoptotic cells with respect to control cells. These findings sugge
st that the post-translational arginylation of proteins may be involved in
programmed cell death.