Pig liver translational initiation factor eif 2 amino terminal amino acid sequences of alpha and gamma subunits and the phosphorylation site structure

Suzuki, H.; Mukouyama, E.B.

Agricultural and Biological Chemistry 52(6): 1397-1408


ISSN/ISBN: 0002-1369
Accession: 006121960

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Eukaryotic initiation factor eIF-2 has key roles in the initiation of protein synthesis. This work describes a partial characterization of pig liver eIF-2 and the phosphorylation site sequence for the .alpha. subunit. Our pig liver eIF-2 was composed of .alpha. and .gamma. subunits. The N-terminal sequences of these subunits were analyzed by an automated Edman degradation. Forty residues of the N-terminal sequences of the .alpha. subunit were identified; they were mostly hydrophobic amino acids. On the other hand, we identified only 19 residues of the N-terminal sequence of the .gamma. subunit, since pig liver eIF-2.gamma. contained a minor component having a sequence lacking the N-terminal Ala-Gly of the .gamma. subunit. Exhaustive tryptic digestion of [32P]-and [3H]carboxymethyl-labeled eIF.tau.2.alpha. produced one major phosphopeptide. The peptide was purified by one dimensional thin-layer chromatography and high performance liquid chromatography. The sequence of the peptide was Ser-Glu-Leu-Ser(P)-Arg-Arg.