Distribution of NG, NG-dimethylarginine in nuclear protein fractions

Nuclear proteins have been fractionated into five distinct classes according to their extractability from rat liver nuclei at different pH and salt concentrations. The fractions have been analyzed for their amino acid composition which shows the presence of N^G, N^G-dimethylarginine, in sizable amount, in non-histone nuclear proteins (NHNP). This modification is most prominent in proteins which are found associated with rapidly-labeled heterogeneous RNA (HnRNP proteins).     

Interaction of molybdenum with human erythrocyte membrane proteins

This study describes the interaction of molybdenum with blood components. Molybdenum-99 was added to blood, and after four washings, 3% of the total radioactivity was found in red cells. More specifically, the radioactivity was determined to be associated with the cell membrane. Molybdenum-99 in the +VI form did not interact with the human erythrocyte membrane; however, Mo(V) forms did interact. Of five different compounds, the highes uptake was observed with a brown Mo(V)-ascorbate complex generated from Mo(VI) and ascorbic acid in the molar ratio 1∶20. A membrane suspension of Mo-ascorbate-treated human erythrocytes was prepared and the solubilized proteins were separated on a polyacrylamide gel in the presence of sodium dodecyl sulfate (SDS). Molybdenum-99 binding to spectrin was demonstrated, as well as some minor interactions with membrane hemoglobin and bands 6 and 8.     

Primary structure of mitochondrial glutamic oxaloacetic transaminase from rat liver: Comparison with that of the pig heart isozyme

The complete amino acid sequence of the mitochondrial glutamic oxaloacetic transaminase isozyme from rat liver is presented. The sequence contained 401 amino acid residues, 10 of which are methionine. Cyanogen bromide cleavage of mitochondrial glutamic oxaloacetic transaminase produced 12 peptides, one of which contained an internal homoserine residue resulting from incomplete cleavage by cyanogen bromide. The calculated molecular weight was 44,358. The sequence showed 94% homology with that of the corresponding isozyme from pig heart. These findings support the conclusion that the rate of evolution of the mitochondrial isozymes is lower than that of their cytosolic isozymes.     

DNA sequence analysis of the defective interfering particles of bacteriophage f1.

Restriction mapping and nucleotide sequence analysis of several defective, interfering particles of bacteriophage f1 are described. These particles contain the nucleotide sequences corresponding to the carboxyl terminus of gene IV and the amino-terminus of gene II and the intergenic space between them. Tandem duplication of a portion of this intergenic space generates defective particles with novel nucleotide sequences not found in wild-type f1. This duplication is shown to contain the origin of complementary strand synthesis. Our results suggest that the duplication occurs at the site of gene II protein action, i.e. the origin of viral strand synthesis. A model is presented for the generation of these duplications in defective particles.     

Mitochondrial mutagenesis in Saccharomyces cerevisiae. III. Nitrous acid.

Nitrous acid (NA) induced mutations efficiently in mitDNA, conferring resistance to erythromycin and weakly induces mit- mutations. In some strains of yeast it also enhanced rho- mutations. The frequencies of nuclear and mitochondrial mutations induced with NA are compared.     

Metal-directed affinity labeling of zinc(II), cobalt(II) and cadmium(II) horse liver alcohol dehydrogenases

The active site metal in horse liver alcohol dehydrogenase has been studied by metal-directed affinity labeling of the native zinc(II) enzyme and that substituted with cobalt(II) or cadmium(II). Reversible binding of bromoimidazolyl propionic acid to the cobalt enzyme blueshifts the visible absorption band originating from the catalytic cobalt atom at 655 to 630 nm. Binding of imidazole to the cobalt(II) enzyme redshifts the 655 nm band to 667 nm. Addition of bromoimidazolyl propionic acid blueshifts this 667 nm band back to 630 nm. This proves direct binding of the label to the active site metal in competition with imidazole. The affinity of the label for the reversible binding site in the three enzymes follows the order Zn ? Cd ? Co. After reversible complex formation, bromoimidazolyl propionic acid alkylates cysteine-46, one of the protein ligands to the active site metal. The nucleophilic reactivity of this metal-mercaptide bond in each reversible complex follows the order Co ? Zn ? Cd.     

Rat and human embryo and post-natal sera contain a potent endogenous competitor of estrogen-rat alpha-fetoprotein interactions

A highly active inhibitor of the binding of estrone and estradiol-17β to rat alpha-fetoprotein is demonstrated for the first time in embryo, immature and adult rat sera as well as in fetal and adult human sera. The competitive character and the narrow specificity of this inhibition effect is shown. The major compound responsible for this activity is isolated by successive column Sephadex LH₂₀ and thin layer chromatography : it is characterized as a nonpolar, nonphenolic, dialysable and thermostable substance, unreactive towards anti-estrone and anti-estradiol-17β anti-bodies. The possible biological role of an endogenous non-estrogen ligand of rodent fetoproteins is discussed.     

Discontinuous DNA replication: accumulation of Simian virus 40 DNA at specific stages in its replication.

The number of proline residues in a protein should have very marked consequences for the rates of protein unfolding and refolding according to the model proposed by Brandts et al. (1975). Kinetic simulations of this model indicate that the half-time for refolding of a polypeptide chain with 20 proline residues should be greater than 10 minutes and should increase by about an order of magnitude for each additional 10 proline residues. Various means are considered by which the rate of protein folding in vivo and in vitro might be increased.     

The restoration of the T-lymphoid system of nude mice: lower efficiency of nonlymphoid, epithelial thymus grafts.

The T-cell deficiency of nude mice is due to an abnormal differentiation of the thymus epithelium; it can be persistently corrected by grafting a neonatal thymus. However, grafted adult thymuses or epithelial thymuses are not repopulated by large numbers of host-derived lymphocytes, as is the case when a whole neonatal thymus is grafted. Furthermore, the repopulation of the spleen and lymph nodes by T cells is less pronounced than after whole neonatal thymus transplantation, and the restoration of the reactivity to T-cell mitogens is irregular. Therefore, the integrity and the age of the thymus graft are important for a good restoration of the T-lymphoid system of congenitally athymic animals.     

Gene fusion vectors based on the gene for staphylococcal protein A

Two plasmid vectors, containing the gene coding for staphylococcal protein A and adapted for gene fusion, have been constructed. These vectors will allow fusion of any gene to the protein A gene, thus giving hybrid proteins which can be purified, in a one-step procedure, by IgG affinity chromatography. As an example of the practical use of such vectors, the protein A gene has been fused to the lacZ gene of Escherichia coli. E. coli strains containing such plasmids produce hybrid proteins with both IgG binding and β-galactosidase activities. The hybrid protein(s) can be immobilized on IgG-Sepharose by its protein A moiety with high efficiency without losing its enzymatic activity and they can be eluted from the column by competitive elution with pure protein A. The fused protein(s) also binds to IgG-coated microtiter wells which means that the in vivo product can be used as an enzyme conjugate in ELISA tests.