The 90-kDa component of reticulocyte heme-regulated eIF-2 alpha (initiation factor 2 alpha-subunit) kinase is derived from the beta subunit of spectrin.
Antibodies from three different lines of monoclonal hybridomas crossreact with both the beta subunit of spectrin and the 90-kDa peptide present in highly purified preparations of the heme-controlled eIF-2 alpha (initiation factor 2 alpha-subunit) kinase from rabbit reticulocytes. Antibodies from two of the three lines enhance the enzymatic activity of the kinase preparation for phosphorylation of the alpha subunit of eukaryotic translational initiation factor 2 (eIF-2) and for phosphorylation of the 100-kDa peptide thought to be a peptide of the kinase that is phosphorylated during its activation. Also, it is shown that both the beta subunit of spectrin and the 90-kDa peptide can be phosphorylated by two protein kinases from reticulocytes, the catalytic subunit of cAMP-dependent protein kinase and a cAMP-independent protein kinase similar to casein kinase II. Furthermore, a phosphorylated 90-kDa peptide can be derived from phosphorylated beta subunit of spectrin by tryptic proteolysis. We conclude that the 90-kDa peptide is derived by proteolysis from the beta subunit of spectrin, probably from its carboxyl terminus, and suggest that the heme-sensitive eIF-2 alpha kinase, like the 56-kDa phosphatase [Wollny, E., Watkins, K., Kramer, G. & Hardesty, B. (1984) J. Biol. Chem. 259, 2484-2492], is associated with an element of the membrane skeleton in intact reticulocytes.
W
W
Kudlicki
S
S
Fullilove
G
G
Kramer
B
B
Hardesty
D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000032:analysis; D006418:Heme / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008970:Molecular Weight; D011494:Protein Kinases / Q000097:blood* / Q000276:immunology; D011817:Rabbits; D012156:Reticulocytes / Q000201:enzymology*; D013049:Spectrin / Q000276:immunology / Q000378:metabolism*; D019892:eIF-2 Kinase
D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D000939:Epitopes; D046911:Macromolecular Substances; D013049:Spectrin; D006418:Heme; D011494:Protein Kinases; D019892:eIF-2 Kinase