Identification of two messenger RNA cap binding proteins in wheat germ. Evidence that the 28-kDa subunit of eIF-4B and the 26-kDa subunit of eIF-4F are antigenically distinct polypeptides.
Previous work has shown that eukaryotic initiation factor (eIF)-4B from wheat germ is a complex containing two subunits, 80 and 28 kDa, and eIF-4F from wheat germ is a complex containing two subunits, 220 and 26 kDa (Lax, S., Fritz, W., Browning, K., and Ravel, J. (1985) Proc. Natl. Acad. Sci. U. S. A. 82, 330-333). Here we show that both the 28-kDa subunit of eIF-4B and the 26-kDa subunit of eIF-4F cross-link to the 5' terminus of capped and oxidized satellite tobacco necrosis virus RNA in the absence of ATP and that the cross-linking of both polypeptides is inhibited by m7GDP. Several lines of evidence indicate that the 28-kDa and the 26-kDa cap binding proteins of eIF-4B and eIF-4F are antigenically distinct polypeptides. Rabbit polyclonal antibodies raised to intact eIF-4B or to the isolated 28-kDa subunit of eIF-4B react strongly with the 28-kDa subunit of eIF-4B on immunoblots, but show only a very weak reaction with the 26-kDa subunit of eIF-4F under the same conditions. In addition, a mouse monoclonal antibody was obtained that reacts strongly with the 26-kDa subunit of eIF-4F but does not react with the 28-kDa subunit of eIF-4B. Evidence is presented also which indicates that the higher molecular weight subunits of eIF-4B and eIF-4F are antigenically distinct. Rabbit polyclonal antibodies raised to intact eIF-4B or the isolated 80-kDa subunit inhibit eIF-4B-dependent polypeptide synthesis but do not inhibit eIF-4F-dependent polypeptide synthesis. Rabbit polyclonal antibodies raised to eIF-4F inhibit eIF-4F-dependent polypeptide synthesis but do not inhibit eIF-4B-dependent polypeptide synthesis.
D000906:Antibodies / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000276:immunology; D002352:Carrier Proteins / Q000032:analysis*; D000939:Epitopes / Q000276:immunology; D039562:Eukaryotic Initiation Factor-4F; D039642:Eukaryotic Initiation Factors; D006153:Guanosine Diphosphate / Q000494:pharmacology; D007118:Immunoassay; D010448:Peptide Initiation Factors / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D010942:Plant Viruses / Q000235:genetics; D010944:Plants / Q000032:analysis*; D039381:RNA Cap-Binding Proteins; D012315:RNA Caps; D012367:RNA, Viral / Q000378:metabolism; D012526:Satellite Viruses / Q000235:genetics; D014908:Triticum
D000906:Antibodies; D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D000939:Epitopes; D039562:Eukaryotic Initiation Factor-4F; D039642:Eukaryotic Initiation Factors; D010448:Peptide Initiation Factors; D039381:RNA Cap-Binding Proteins; D012315:RNA Caps; D012367:RNA, Viral; C031799:eIF-4B; D006153:Guanosine Diphosphate