Mammalian ribosomal protein: analysis by electrophoresis on polyacrylamide gel.

Ribosomal protein from five mammalian tissues when analyzed by discontinuous electrophoresis on polyacrylamide gel at pH 4.5 yielded 24 bands. Densitometric tracings indicated that the patterns of the basic ribosomal proteins from the several tissues were qualitatively similar. Protein from Escherichia coli ribosomes analyzed at pH 4.5 gave 29 bands, and the pattern was different from that of mammalian ribosomal protein. No distinct band was found when mammalian ribosomal protein was analyzed at pH 8.3 (acidic proteins). Ribosomal protein from Escherichia coli gave eight bands at pH 8.3. Thus, the structure of the genes responsible for synthesis of ribosomal protein in several mammalian tissues is the same, and different genes direct synthesis of ribosomal protein in bacteria.

Reticulocyte membrane transferrin receptors.

A membrane protein with specific transferrin binding activity has been isolated from rabbit reticulocytes. The isolation procedure involved the immunoprecipitation by antibody to transferrin of transferrin-receptor complexes from reticulocyte membrane proteins which had been solubilized with nonionic detergent. Receptor dissociated from the antibody-transferrin-receptor complexes could bind transferrin saturably and reversibly. It migrated electrophoretically as a single band of glycoprotein with an estimated molecular weight of approximately 180 000 which was reduced to around 93 000 following complete dissociation with dithiothreitol.

Equal stabilities of normal beta globin and nontranslatable beta0 -39 thalassemic transcripts in cell-free extracts.

Patients with beta zero thalassemia arising from premature terminator codon mutations in the gene for beta globin do not produce beta globin protein; these individuals also exhibit a decreased amount of beta globin mRNA in their erythroid cells. The absence of beta globin protein is readily explained by the inability of the beta zero-39 mRNA to be translated. The decrease in beta globin mRNA has been attributed to either decreased cytoplasmic stability of the nontranslatable decreased cytoplasmic stability of the nontranslatable mRNA or to an undefined nuclear lesion. To compare directly the relative stabilities of normal and beta zero-39 thalassemic globin transcripts, we prepared normal and thalassemic beta globin pre-mRNAs and mRNAs using cloned DNA templates and the SP6 promoter-polymerase system. The stability of the transcripts was assessed by incubation in various cell-free extracts. Our results indicate that although the stabilities of the beta globin transcripts varied considerably from one extract to another the stabilities of the beta zero-39 thalassemic pre-mRNAs and mRNAs were equal to those of normal beta globin mRNAs in every extract tested.