The 90-kDa Component of Reticulocyte Heme-Regulated eIF-2α (Initiation Factor 2 α -Subunit Kinase is Derived from the β Subunit of Spectrin

Antibodies from three different lines of monoclonal hybridomas crossreact with both the β subunit of spectrin and the 90-kDa peptide present in highly purified preparations of the heme-controlled eIF-2α (initiation factor 2 α -subunit) kinase from rabbit reticulocytes. Antibodies from two of the thr...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1985-08, Vol.82 (16), p.5332-5336
Main Authors: Kudlicki, Wieslaw, Fullilove, Susan, Kramer, Gisela, Hardesty, Boyd
Format: Article
Language:English
Subjects:
Antibodies
Biochemistry
Chromatography
Enzymes
Gels
Monoclonal antibodies
Peptide initiation factors
Phosphorylation
Reticulocytes
Skeleton
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Summary:Antibodies from three different lines of monoclonal hybridomas crossreact with both the β subunit of spectrin and the 90-kDa peptide present in highly purified preparations of the heme-controlled eIF-2α (initiation factor 2 α -subunit) kinase from rabbit reticulocytes. Antibodies from two of the three lines enhance the enzymatic activity of the kinase preparation for phosphorylation of the α 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 β 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 β subunit of spectrin by tryptic proteolysis. We conclude that the 90-kDa peptide is derived by proteolysis from the β subunit of spectrin, probably from its carboxyl terminus, and suggest that the heme-sensitive eIF-2α 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.
ISSN:0027-8424