Comparison of mRNA binding by Met-tRNAf binding protein and mRNA-associated proteins.
One of the heterogeneous mRNA binding activities in the 0.5 M KCl eluate of rabbit reticulocyte polyribosomes co-purified to apparent homogeneity through phosphocellulose and DEAE-cellulose chromatography and isoelectric focusing with the GTP-dependent Met-tRNAf binding protein. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis following iodination revealed putative subunits of 51,000 and 39,000 apparent molecular weights. Specificity of mRNA binding by this protein was suggested since the ability of poly(A)-rich mRNA to compete for binding of [3H]poly(A)-rich mRNA exceeded by 10- to 100-fold that of most natural or synthetic RNAs tested, except for the hybrid poly(G) - poly(C) which was almost as effective, and poly(G), which was more effective, at competing for protein-dependent binding. The mRNA binding activity exhibited complete GTP independence and no apparent divalent cation requirement. GDP inhibited Met-tRNAf binding but neither GDP, GMP, nor 7-methylguanosine 5'-monophosphate inhibited mRNA binding by this protein. Similar data were obtained with respect to the ability of natural or synthetic RNAs to compete for binding of [3H]poly(A)-rich mRNA by proteins associated with purified rabbit reticulocyte polyribosomal mRNA-protein particles; while poly(A) was an ineffective competitor, poly(G) was more effective than even mRNA at competing for protein-dependent binding. No significant binding of Met-tRNAf by mRNA-protein particles was detected. Polyacrylamide gel electrophoresis following reduction of mRNA-protein particles revealed apparent co-migration of a major protein with one subunit of the GTP-dependent Met-tRNAf binding protein, but no protein comparable to the 39,000 dalton subunit protein.
D000818:Animals; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism; D007700:Kinetics; D008715:Methionine; D008970:Molecular Weight; D011131:Polyribonucleotides / Q000378:metabolism; D011132:Polyribosomes / Q000378:metabolism; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism
D002352:Carrier Proteins; D011131:Polyribonucleotides; D012333:RNA, Messenger; D012261:Ribonucleoproteins; D012269:Ribosomal Proteins; D012343:RNA, Transfer; D008715:Methionine