6-DIAZO-5-OXO-L-NORLEUCINE INHIBITION OF ESCHERICHIA COLI

Coggin, J. H., Jr. (The University of Chicago, Chicago, Ill.), and W. R. Martin. 6-Diazo-5-oxo-l-norleucine inhibition of Escherichia coli. J. Bacteriol. 89:1348-1353. 1965.-The glutamine analogue 6-diazo-5-oxo-l-norleucine (DON) induced filaments and spheroplasts in Escherichia coli during the transition of sensitive populations to a state of resistance. Resistance developed at a frequency suggesting mutant selection. The morphology of cells resistant to 100 mug of DON per ml was indistinguishable from that of sensitive cells. DON-resistant cells exhibited an extended growth lag when cultured in the absence of the drug. This extended lag could be reduced to the lag time of parent sensitive cells by a combination of d-glucosamine and inosine or by DON. Viable counts during the lag period of resistant cells indicate that this lag results from a decrease in the number of cells during the first 2 hr of incubation. A combination of d-glucosamine and inosine was required for complete prevention of the DON inhibition of sensitive cells. The results indicate that DON not only inhibits de novo purine biosynthesis but that it also prevents hexosamine synthesis and, ultimately, cell-wall synthesis in E. coli.

STUDIES ON HUMAN ANTIBODIES. 3. AMINO ACID COMPOSITION OF FOUR ANTIBODIES FROM ONE INDIVIDUAL

Antilevan, antidextran, antiteichoic acid, anti-"A" and normal γG, all isolated from a single human, as well as pooled γG and γM, were analyzed for amino acid content. Differences ranging from 7 to 32 residues were found among these antibodies in glycine, valine, leucine, tyrosine, arginine, lysine, and threonine content. These conspicuous differences in amino acid composition were not correlated with the Gm type of these antibodies. Hydroxylysine was found in two of the four antibodies, antidextran and antiteichoic acid, and in γM- immunoglobulin. No hydroxylysine was found in γG- globulins. These findings probably account for discrepancies in the literature concerning the occurrence of this residue in antibody protein.

SMALL-SCALE ISOLATION OF FERRITIN FOR THE ASSAY OF THE INCORPORATION OF 14C-LABELLED AMINO ACIDS

1. A new procedure is described for the isolation of pure ferritin from small amounts of tissue. After the removal of most of the tissue proteins by heat coagulation, the ferritin fraction was chromatographed successively on CM-cellulose and Sephadex G-200. 2. The isolated ferritin appeared to be free from other proteins, as judged by its sedimentation pattern in the ultracentrifuge, by electrophoresis on polyacrylamide gel and by immunoelectrophoresis. 3. After the injection of [(14)C]leucine into a series of rats, the specific activity of liver ferritin isolated by the new procedure bore a constant relationship to that of liver ferritin separated by antigen-antibody precipitation. The procedure can thus be used to obtain ferritin of suitable purity for studies of amino acid incorporation. 4. The new procedure can be used to measure the total ferritin protein content of a tissue. It is not possible to use ultraviolet absorption for the measurement of ferritin protein because of considerable interference from the iron that it contains.

THE STIMULATION BY TREATMENT IN VIVO WITH TRI-IODOTHYRONINE OF AMINO ACID INCORPORATION INTO PROTEIN BY ISOLATED RAT-LIVER MITOCHONDRIA

1. Normal and thyroidectomized rats were treated with near-physiological doses of tri-iodothyronine. Liver mitochondria were isolated and incubated with radioactive amino acids. In normal rats tri-iodothyronine caused only a slight stimulation of incorporation into mitochondrial protein, but in thyroidectomized animals the incorporation was doubled. 2. There was a lag period of about 36 hr. after injection and the maximum effect was observed after 2 days. 3. Direct addition of tri-iodothyronine to the incubation medium had no effect on mitochondrial incorporation. 4. The incorporation was not due to bacterial, nuclear, lysosomal or microsomal contamination and the labelled particles had sedimentation properties identical with those of mitochondria, as followed by suitable enzyme markers. 5. Thyroid hormone treatment did not cause any marked alterations in the pattern of labelling of submitochondrial fractions and in all cases the most radioactive protein was in an insoluble lipid-rich fraction. The amino acid compositions of the total mitochondrial protein and the more radioactive lipoprotein were also unaltered. 6. Increases in the content of RNA and various cytochromes per mg. of mitochondrial protein were observed after treatment with tri-iodothyronine. These occurred slightly later than the stimulation of amino acid incorporation. 7. No uncoupling of oxidative phosphorylation was observed and the ATP production per mg. of mitochondrial protein increased. 8. It was concluded that tri-iodothyronine stimulated amino acid incorporation into mitochondrial protein and that the result is consistent with the view that treatment with thyroid hormone results in an enhanced selective synthesis of mitochondrial respiratory units.

THE ISOLATION AND PROPERTIES OF CARDIAC RIBOSOMES AND POLYSOMES

1. A method is described by which good yields of ribosomes and polysomes free of contamination by submitochondrial fragments can be prepared from rat cardiac muscle. These preparations are capable of incorporation of amino acids into protein in vitro. 2. The ribosome preparation consists of 32% of monomeric ribosomes and 68% of ribosomal aggregates or polysomes. The polysome preparation has a decreased monomeric content. Dimers, trimers, tetramers, pentamers and larger components can be differentiated. 3. The polysome aggregate structure is degraded to monomeric ribosomes on incubation with small amounts of ribonuclease or by preparation in the absence of Mg(2+) ions. The degradation in the absence of Mg(2+) ions was not reversible and drastically decreased the incorporation of amino acids in vitro. 4. The cardiac ribosomes contained two major RNA species sedimenting at 19s and 28s in a 1:2.4 ratio. 5. The RNA/protein ratio of cardiac ribosomes and polysomes was consistently lower than that of similar preparations from liver. The concentrations of Na(+) and K(+) ions present during preparation had a great effect on the RNA/protein ratio. 6. Optimum conditions for the incorporation of amino acids into protein in vitro are reported. Cardiac ribosomes have a lower rate of incorporation of amino acids in vitro than liver ribosomes. 7. Heart cell sap is less active than liver cell sap: evidence is presented that a factor, present in liver cell sap and concerned with stimulating the synthesis of the peptide chain, is lacking in heart cell sap. 8. Pulse-labelling of perfused hearts followed by examination of the subcellular structures showed that the ribosomal fraction was the most active in the incorporation of amino acids in vitro.