title: Removal of beta subunit of the eukaryotic polypeptide chain initiation factor 2 by limited proteolysis.
abstract: It is generally considered that the eukaryotic polypeptide chain initiation factor 2 (eIF-2) from rabbit reticulocytes consists of three nonidentical subunits termed alpha, beta, and gamma, in order of increasing molecular weight. However, a recent report [Stringer, E. A., Chaudhuri, A., Valenzuela, D. & Maitra, U. (1980) Proc. Natl. Acad. Sci. USA 77, 3356-3359] suggested that this factor is made up of only two subunits. In this paper we show that limited proteolysis of rabbit reticulocyte eIF-2 leads to loss of the beta subunit. This modified eIF-2 has the same activity as the native factor in promoting ternary (eIF-2.GTP.Met-tRNAi) and 40S (eIF-2.GTP.Met-tRNAi.40S ribosome) initiation complex formation. Like native eIF-2, the protease-treated factor can restore translation in heme-deficient lysates. On the other hand, the treated factor is less stable than the native protein.
mesh_terms: D000818:Animals; D015852:Eukaryotic Initiation Factor-2; D039621:Eukaryotic Initiation Factor-3; D006358:Hot Temperature; D046911:Macromolecular Substances; D008970:Molecular Weight; D010442:Peptide Chain Initiation, Translational; D010447:Peptide Hydrolases / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D013329:Structure-Activity Relationship; D014357:Trypsin / Q000378:metabolism
chemical_list: D015852:Eukaryotic Initiation Factor-2; D039621:Eukaryotic Initiation Factor-3; D046911:Macromolecular Substances; D010448:Peptide Initiation Factors; D011506:Proteins; D010447:Peptide Hydrolases; D014357:Trypsin