Purification of the messenger RNA cap-binding protein using a new affinity medium.
The p-aminophenyl gamma-ester of 7-methylguanosine 5'-triphosphate (m7GTP) was synthesized and coupled to Sepharose 4B. A 0.5 M salt extract of rabbit reticulocyte ribosomes was passed over a column containing the affinity medium. After extensive washing, a solution of m7GTP was passed through the column, and a single polypeptide species of 24 kilodaltons (kDa) was eluted. This had an electrophoretic mobility identical with that of the mRNA cap-binding protein. This assignment was confirmed by the fact that the eluted material was enriched nearly 200-fold in the ability to specifically bind 32P-labeled capped oligonucleotides. A control affinity medium consisting of GTP similarly coupled to Sepharose failed to retain the 24-kDa species. The postribosomal supernatant fraction yielded slightly more of the 24-kDa species than the ribosomal wash fraction when passed over this affinity medium.
D000818:Animals; D002352:Carrier Proteins / Q000302:isolation & purification*; D002846:Chromatography, Affinity / Q000379:methods; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D007202:Indicators and Reagents; D039381:RNA Cap-Binding Proteins; D012315:RNA Caps; D011817:Rabbits; D012156:Reticulocytes / Q000032:analysis; D012270:Ribosomes / Q000032:analysis
D002352:Carrier Proteins; D007202:Indicators and Reagents; D039381:RNA Cap-Binding Proteins; D012315:RNA Caps; D006160:Guanosine Triphosphate; C040518:gamma-(4-aminophenyl) 7-methylguanosine 5'-triphosphate