The activity of the acidic phosphoproteins from the 80 S rat liver ribosome.
The selective removal of acidic phosphoproteins from the 80 S rat liver ribosome was accomplished by successive alcohol extractions at low salt concentration. The resulting core ribosomes lost over 90% of their translation activity and were unable to support the elongation factor 2 GTPase reaction. Both activities were partially restored when the dialyzed extracts were added back to the core ribosome. The binding of labeled adenosine diphosphoribosyl-elongation factor 2 to ribosomes was also affected by extraction and could be reconstituted, although not to the same extent as the GTPase activity associated with elongation factor 2 in the presence of the ribosome. The alcohol extracts of the 80 S ribosome contained mostly phosphoproteins P1 and P2 which could be dephosphorylated and rephosphorylated in solution by alkaline phosphatase and protein kinase, respectively. Dephosphorylation of the P1/P2 mixture in the extracts caused a decrease in the ability of these proteins to reactivate the polyphenylalanine synthesis activity of the core ribosome. However, treatment of the dephosphorylated proteins with the catalytic subunit of 3':5'-cAMP-dependent protein kinase in the presence of ATP reactivated the proteins when compared to the activity of the native extracts. Rabbit antisera raised against the alcohol-extracted proteins were capable of impairing both the polyphenylalanine synthesis reaction and the elongation factor 2-dependent GTPase reaction in the intact ribosomes.
D000818:Animals; D002458:Cell Fractionation; D004591:Electrophoresis, Polyacrylamide Gel; D020963:GTP Phosphohydrolase-Linked Elongation Factors / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D051381:Rats; D012270:Ribosomes / Q000378:metabolism* / Q000648:ultrastructure
D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors; D010750:Phosphoproteins; D020963:GTP Phosphohydrolase-Linked Elongation Factors