Ontogeny of ppp(A2'p)nA-binding protein in mouse brain.

Mouse brain tissue extracts at various stages of development show a drastic change in the specific activity of pp(A2'p)3A-[32P]pCp binding protein. Identification of the ppp(A2'p)3A-[32P]pCp binding protein was established by (i) binding to the specific ligand ppp(A2'p)3A-[32P]pCp, (ii) displacement of binding by nanomolar concentrations of pppA(pA)3, and (iii) affinity labeling techniques in which periodate oxidized ppp(A2'p)3A-[32P]pC was specifically cross-linked to a protein with a molecular weight of 85000. These data suggest that the ppp(A2'p)3A-[32P]pCp protein is closely associated with the process of cellular proliferation and differentiation.