Assignment of the β-Subunit of Wheat eIF2 by Protein and DNA Sequence Analysis and Immunoanalysis

Wheat germ initiation factor 2 (eIF2), like mammalian and yeast eIF2, contains three nonidentical subunits. The estimated molecular weights for the wheat subunits are 38,000 (p38), 42,000 (p42), and 50,000 (p50). Peptide sequence was obtained for the p38 subunit of wheat eIF2 and the resulting amino acid sequence suggested that it was actually the equivalent of the mammalian β-subunit. A wheat sprout cDNA expression library was screened with antibody affinity purified to the p38 subunit. The DNA sequence of the clones obtained also indicated that the p38 subunit was the equivalent to the mammalian β-subunit. The wheat p38 subunit was then expressed inEscherichia coliand antibodies raised to the purified recombinant protein. Only the p38 subunit of purified wheat germ eIF2 reacted with the antisera. The p38 subunit of wheat eIF2 is therefore the equivalent of mammalian eIF2β.