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Biomedical subjects

C C Levy

Publications and source records attributed to C C Levy.

At least 19 recordsLinked to original sources
PubMed1978

Effect of RNA tumor virus-specific protein p30 on reverse transcriptase. Intraspecies and interspecies interaction between reverse transcriptase and p30.

Reverse transcriptase and p30 were purified from various retroviruses and the intra- and interspecific interaction between the two proteins were studied. The intraspecific complex stimulates [3H]TMP incorporation into (dT)12.(rA)n severalfold above that of the enzyme itself whereas DNA synthesis in the presence of the interspecific complex can stimulate DNA synthesis about 1.5-fold. The sedimentation rate value of the intraspecies complex varies between 12 and 16 S with an estimated molecular weight of 400,000. The molar ratio of p30:reverse transcriptase within the complex is 8:1. Both complexes can be dissociated into their original protein components by exposure to salt (kcl) solution, except that 0.3 M KCl will dissociate the interspecies complex whereas 0.8 M KCl is required for dissociation of the intraspecies complex. Competition studies in which an interspecies complex was exposed to p30 autologous to reverse transcriptase within the complex resulted in the displacement of the heterologous (p30) protein and the formation of a new intraspecific complex.

Molecular Weight↗
PubMed1978

Possible sites of origin of human plasma ribonucleases as evidenced by isolation and partial characterization of ribonucleases from several human tissues.

The ribonucleases (RNases) present in a number of human tissues, including heart, brain, lung, and kidney, were purified, partially characterized, and compared in their properties to the previously described RNases from human liver, spleen, pancreas, and serum. The enzymes appeared to fall into two major classes: liver-spleen type RNase and plasma-type RNase. These two types of enzymes were present in varying proportions in all tissues examined. The extent to which the tissues studied possibly contribute to serum RNase levels is discussed.

Brain↗
PubMed1977

Complexing Rauscher leukemia virus reverse transcriptase with human plasma ribonuclease from Hodgkin's disease patients.

Human ribonucleases were purified from the sera of Hodgkin's disease patients by sequential column chromatography. The purified enzyme interacted with reverse transcriptase of Rauscher leukemia virus and formed an additive complex of Mr = 130,000. RNase and oligo(dG)-directed reverse transcriptase activities were diminished in the complex. The complex could be dissociated with the subsequent restoration of both activities in the presence of spermidine. The molecular weight of the complex suggest that the 2 RNase molecules bind to a single reverse transcriptase molecule.

Hodgkin Disease↗
PubMed1977

The immunological characterization of several human ribonucleases by using primary binding tests.

RNAases (ribonucleases), purified from four human tissues, as well as bovine pancreatic RNAase (RNAase A), were studied by immunodiffusion methods and by two different primary binding tests. The enzymes fell into two groups immunologically, those purified from plasma and pancreas in one and those from spleen and liver in the other. No antigenic cross-reaction between the two groups was detected by any of the immunoassays used. There was a slight antigenic cross-reaction between the human and bovine pancreatic RNAases. The liver and spleen RNAases were immunologically identical by all criteria used, whereas a small but consistent antigenic difference between the human plasma and human pancreas enzymes was detected. The significance of this difference between the human plasma and pancreas RNAases is discussed in relation to similarities and differences in their properties.

Animals↗
PubMed1977

Influence of renal insufficiency on levels of serum ribonuclease in patients with multiple myeloma.

Serum RNase levels were measured in 34 patients with multiple myeloma and compared with 51 normal controls and 28 non-myeloma patients on chronic hemodialysis. Nineteen of the myeloma patinets with creatinine clearance (CCr) greater than 50 ml/minute had mean serum RNase levels that were statistically indistinguishable from those of the normal controls. The 15 myeloma patinets with CCr less than 50 ml/minute had mean RNase levels much higher than normal controls or myeloma patients with normal renal function. Patients without myeloma but on hemodialysis for chronic renal failure of varied etiologies had markedly elevated serum RNase levels. A strong correlation between RNase levels and renal insufficiency, as measured by CCr, has thus been demonstrated. In addition, case histories of 5 representative myeloma patients were analyzed in greater detail; they illustrated the rise and fall of RNase levels as a function of the status of their renal insufficiency, regardless of the extent of the underlying myeloma. We concluded that the serum RNase level was an indicator of renal function, and was not a biomarker either for the presence or extent of the plasma cell tumor.

Creatinine↗
PubMed1977

RNase activity in human interferon preparations.

The level of RNase activity in human interferon preparations was examined. Although sequential purification of interferon resulted in nearly a 300-fold increase in specific activity, RNase-specific activity remained more or less constant. The implications of this finding for the analyses of the mode of action of interferon are discussed.

Humans↗
PubMed1976

Purification of human spleen ribonuclease by immunoabsorption. Similarity of the enzyme with human liver ribonuclease.

Human spleen RNase was purified using an immunoabsorbant produced with anti-human liver RNase serum. The purification was more rapid than the procedure used to purify the liver RNase, yet the final specific activity was similar. Problems encountered previously using immunoabsorbants to purify enzymes were to a large degree avoided by injecting only microgram amounts of human liver RNase directly into the popliteal lymph nodes of rabbits, thereby producing a low avidity antibody. The low avidity antibody permitted elution from the immunoabsorbant with only dilute citrate buffer and without significant denaturation. An examination of crude spleen homogenates did not reveal any other RNase to be present except that which bound to the antibody. The enzyme was found to be antigenically unrelated to the human plasma RNase. A comparison of the physical properties of the human spleen enzyme with those of the human liver enzyme did not reveal any significant differences.

Calcium↗
PubMed1976

Properties of a human liver ribonuclease. Inhibition by polynucleotides and specificity for phosphodiester bond cleavage to yield purine nucleosides at the 5' termini.

A ribonuclease, purified 2500-fold from human liver, was found to be inactive against synthetic homopolynucleotides, whereas synthetic co-polymers containing adenylic acid were rapidly degraded. The specificity of the RNase is unique in that only purine residues, in a 5:4 ratio of guanylic to adenylic acid, are found at the 5' termini of the degradation products of yeast RNA. No specificity was observed at the 3' termini of the fragments. When analyzed by DEAE-cellulose chromatography, approximately 80% of the oligonucletoides were 4 to 11 residues in length. The hydrolysis of RNA by the liver enzyme, when examined in low ionic strength buffer, could be increased severalfold over control levels by the addition of polyamines. The enzyme was found to exist as two distinct species on sucrose gradients, with molecular weights of 128,000 and 14,000. However, the addition of spermidine to the gradients resulted in the recovery of all the enzyme activity as the smaller species. The polyamines were also shown to reverse the inhibition of the enzyme by the ordered polynucleotides, polyguanylic acid and polyadenylic acid. Inhibition of enzyme activity by the polyadenylic acid segment of various mammalian mRNAs was also demonstrated.

Humans↗
PubMed1976

Stabilization of an RNA molecule by 3'-terminal poly (A)-induced inhibition of RNase activity.

The inhibitory properties of poly(A) on human spleen ribonuclease have been investigated. Hydrolytic activity has been shown to be strongly inhibited by poly(A) contained within RNAs isolated from a variety of natural sources. Furthermore, poly(A) segments of varying length have been covalently linked at the 3' terminus of Escherichia coli 5 S rRNA by polynucleotide phosphorylase in an attempt to construct an in vitro demonstration of the stabilization of RNA which contains poly(A). The extent to which these poly(A) tracts, varying from 4 to 132 nucleotides in length, could inhibit endonucleolytic attack on the 5 S rRNA to which they are linked was found to be dependent upon their length and upon small changes in spermidine concentration. The consequences of these findings are discussed in terms of a possible role for poly(A).

Enzyme Activation↗
PubMed1976

Peptides isolated from Enterobacter nuclease as potential polyamine binding sites.

The Enterobacter nuclease, which cleaves RNA between the 3'-phosphate group of cytidylic acid and the 5'-hydroxyl group of adenylic acid, has been shown to be affected by the polyamines, spermidine, spermine and putrescine. These substances enhance the hydrolytic activity of the enzyme against both poly(C) and yeast RNA. Sperimidine and spermine also reverse the inhibition of the enzyme by the ordered polynucleotides, apparently by removing them from the surface of the enzyme. Treatment of poly(G)-bound peptides (obtained from tryptic digests of poly(G)-bound nuclease) with an excess of spermidine resulted in the isolation of spermidine-bound peptides. Purification of these peptides through ion-exchange chromatography resulted in the isolation of three spermidine-bound peptides which consisted of 17 residues (6 amino acids), 19 residues (10 amino acids), and 12 residues (9 amino acids). The binding ratio of spermidine to peptides varied from 1:1 to 3:1.

Amino Acids↗