J. Biol. Chem., Vol. 262, Issue 20, 9695-9701, Jul, 1987
Identification of spectrin-related peptides associated with the reticulocyte heme-controlled alpha subunit of eukaryotic translational initiation factor 2 kinase and of Mr 95,000 peptide that appears to be the catalytic subunit
W Kudlicki, S Fullilove, R Read, G Kramer and B Hardesty
An isolation procedure for the reticulocyte heme-controlled alpha subunit
of eukaryotic translational initiation factor 2 (eIF-2 alpha) kinase is
described which yields different fractions with kinase activity. Each is
associated with a different spectrin-related peptide as identified by
anti-spectrin monoclonal antibodies. The most abundant of these peptides is
the Mr 90,000 species characterized previously (Kudlicki, W., Fullilove,
S., Kramer, G., and Hardesty, B. (1985) Proc. Natl. Acad. Sci. U.S.A. 82,
5332-5336). Association with the spectrin- related peptides appears to
account for the heterogeneity of the enzyme during its isolation and for
its highly asymmetric structure. Isolated alpha or beta spectrin subunits
as well as the separated homogeneous Mr 90,000 peptide cause an increase in
the initial rate of eIF-2 alpha phosphorylation that is related to a
decrease in Km with little or no effect on Vmax for the phosphorylation
reaction. Fractionation of highly purified eIF-2 alpha kinase preparations
using affinity chromatography on monoclonal anti-spectrin antibodies has
separated eIF- 2 alpha kinase activity from the Mr 100,000 phosphopeptide
which copurifies with the kinase during all other purification steps. A Mr
95,000 peptide, detectable only by photoaffinity labeling with 8-azido-
[alpha 32P]ATP, is shown to be distinct from the Mr 100,000 phosphopeptide
and appears to be the catalytic subunit of the eIF-2 alpha kinase.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?