Regulation of protein synthesis in rabbit reticulocyte lysates. Requirement of initiation factor eIF-2 holoprotein for substrate specificity of heme-regulated protein kinase.
The specificity of the heme-regulated protein kinase (HRI) was investigated further by utilizing the isolated 38,000 Da subunit (alpha subunit) polypeptide of eIF-2 as the substrate. For this purpose, the three subunit polypeptides of eIF-2 (38,000 Da, alpha; 50,000 Da, beta; and 52,000 Da, gamma) were resolved by reversed-phase high performance liquid chromatography (HPLC). Results show that HRI is incapable of phosphorylating the 38,000 Da subunit separated from the other two eIF-2 polypeptides. Data suggest that the substrate specificity of HRI is determined by the quaternary structure assumed by the alpha subunit in association with the other two subunits in the eIF-2 holoprotein.
D000818:Animals; D001798:Blood Proteins; D002474:Cell-Free System; D015852:Eukaryotic Initiation Factor-2; D006418:Heme / Q000494:pharmacology*; D046911:Macromolecular Substances; D010448:Peptide Initiation Factors / Q000097:blood* / Q000302:isolation & purification; D010455:Peptides / Q000302:isolation & purification; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000097:blood*; D011506:Proteins / Q000302:isolation & purification; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism*; D013379:Substrate Specificity
D001798:Blood Proteins; D015852:Eukaryotic Initiation Factor-2; D046911:Macromolecular Substances; D010448:Peptide Initiation Factors; D010455:Peptides; D011506:Proteins; D006418:Heme; D011494:Protein Kinases