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P Blackburn

Publications and source records attributed to P Blackburn.

16 recordsLinked to original sources
PubMed1992

Evaluation of a nisin-based germicidal formulation on teat skin of live cows.

A purified preparation of the nontoxic antimicrobial peptide, nisin (AMBICIN N), was used in the formulation of a germicidal sanitizer suitable for use on cow teats. The germicidal activity of the formulation against mastitis pathogens was measured on teat skin of live cows. The nisin-based formulation gave a mean log reduction of 3.90 against Staphylococcus aureus and 4.22 log reduction against Escherichia coli after exposure for 1 min to the germicide. This activity was comparable with that exhibited by a 1% iodophor teat dip but was significantly greater than that exhibited by the .1 and .5% iodophors and by the .5% chlorhexidine digluconate teat dips. The nisin-based formulation showed little or no potential for skin irritation after multiple application to skin, but iodophor and chlorhexidine digluconate teat dips showed significant potential for skin irritation in comparable studies.

Animals↗
PubMed1986

Amino acid sequence of a basic Agkistrodon halys blomhoffii phospholipase A2. Possible role of NH2-terminal lysines in action on phospholipids of Escherichia coli.

A basic (pI = 10.2) phospholipase A2 of the venom of the snake Agkistrodon halys blomhoffii is one of a few phospholipases A2 capable of hydrolyzing the phospholipids of Escherichia coli killed by a bactericidal protein purified from human or rabbit neutrophil granules. We have shown that modification of as many as 4 mol of lysine per mole of the phospholipase A2, either by carbamylation or by reductive methylation [Forst, S., Weiss, J., & Elsbach, P. (1982) J. Biol. Chem. 257, 14055-14057], had no effect on catalytic activity toward extracted E. coli phospholipids or the phospholipids of autoclaved E. coli. In contrast, modification of 1 mol of lysine per mole of enzyme substantially reduced activity toward the phospholipids of E. coli killed by the neutrophil protein. To explore further the role of lysines in the function of this phospholipase A2, we determined the amino acid sequence of the enzyme and the incorporation of [14C]cyanate into individual lysines when, on average, 1 lysine per molecule of enzyme had been carbamylated. After incorporation of approximately 1 mol of [14C]cyanate per mole of protein, the phospholipase A2 was reduced, alkylated, and exhaustively carbamylated with unlabeled cyanate. The amino acid sequence was determined of the NH2-terminal 33 amino acids of the holoprotein and of peptides isolated after digestion with trypsin and Staphylococcus aureus V-8 protease. The protein contains 122 amino acid residues, 17 of which are lysines. The NH2-terminal region is unique among more than 30 phospholipases A2 previously sequenced because of its high content of basic residues (His-1, Arg-6, and Lys-7, -10, -11, and -15).(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1979

Ribonuclease inhibitor from human placenta: rapid purification and assay.

The ribonuclease inhibitor from human placenta may be isolated in 65% yield (2.5 mg per placenta) in 2 days. The performance of the affinity chromatography on Sepharose-RNase A has been expedited through adaption of the spectrophotometric assay of ribonuclease toward 2',3'-cyclic cytidine monophosphate to determination of the inhibitor activity. The result of these improvements in procedure is increased availability of the ribonuclease inhibitor for study of its chemical properties (Blackburn, P., and Jailkhani, B.L. (1979) J. Biol. Chem. 254, 12488-12493) and for its inclusion into in vitro systems in which inhibition of mammalian neutral ribonucleases is desired.

Female↗
PubMed1979

Role of mammalian RNase inhibitor in cell-free protein synthesis.

Addition of the human placental RNase inhibitor at 10 mu/ml to a mixture of wheat germ extract and translation components, prior to the addition of mRNA from dog pancreas or influenza virus-infected cells, resulted in a significant increase in the yield of proteins synthesized. Analysis of the translation products by sodium dodecyl sulfate/polyacrylamide gel electrophoresis indicated that the inhibitor preferentially increased the yield of the larger proteins. In the presence of the inhibitor, yields of the preprocarboxypeptidases were increased 4.5-fold and yields of preamylase were increased 15-fold. Incubation of the wheat germ extract or individual translation components with dog pancreas mRNA, with or without the placental inhibitor, indicated significant RNase contamination among the fractions. Two other in vitro protein synthesis systems-the reticulocyte lysate system and the Krebs ascites system-were found to contain latent RNase activity (RNase in complex with the inhibitor) and an excess of RNase inhibitor. The addition of placental RNase inhibitor did not increase the yield in these systems, except in those cases in which the RNase contamination approached the amount of endogenous inhibitor. When used during the isolation of rat liver cell fractions, the placental inhibitor increased the yield (as measured by A(260)) of rough microsomes and detached polysomes by 24% and 4.6-fold, respectively. Analysis of translation products indicated that detached polysomes isolated in the presence of the inhibitor were intact; those isolated in the absence of inhibitor were degraded.

Animals↗
PubMed1977

Urinary amino acid excretion by patients with beta-thalassemia.

Twenty-four hour urinary amino acid excretion has been studied in patients with beta-thalassemia (four adult major, two adult intermedia, and three children major). beta-Aminoisobutyric acid was found to be increased (14-fold on the average) in patients with beta-thalassemia without evidence for increase in the excretion of most other amino acids. No correlation of beta-aminoisobutyric acid excretion with the hematological status of the patient was found. Elevated taurine excretion (2-fold) was also noted in the adult patients with beta-thalassemia. Greatly increased excretion of beta-aminoisobutyric acid appears to correlate with a poor prognosis and may reflect generalized tissue catabolism rather than being a specific indicator of ineffective erythropoiesis.

Adolescent↗
PubMed1977

Ribonuclease inhibitor from human placenta. Purification and properties.

A soluble ribonuclease inhibitor from the human placenta has been purified 4000-fold by a combination of ion exchange and affinity chromatography. The inhibitor has been isolated in 45% yield (about 2 mg/placenta) as a protein that is homogeneous by sodium dodecyl sulfate-gel electrophoresis. In common with the inhibitors of pancreatic ribonuclease from other tissues that have been studied earlier, the placental inhibitor is an acidic protein of molecular weight near 50,000; it forms a 1:1 complex with bovine pancreatic RNase A and is a noncompetitive inhibitor of the pancreatic enzyme, with a Ki of 3 X 10(-10) M. The amino acid composition of the protein has been determined. The protein contains 30 half-cystine plus cysteine residues determined as cysteic acid after performic acid oxidation. At pH 8.6 the nondenatured protein alkylated with iodoacetic acid in the presence of free thiol has 8 free sulfhydryl groups. The inhibitor is irreversibly inactivated by sulfhydryl reagents and also by removal of free thiol from solutions of the protein. Inactivation by sulfhydryl reagents causes the dissociation of the RNase - inhibitor complex into active RNase and inactive inhibitor.

Amino Acids↗
PubMed1977

Explanation of the observation of pancreatic ribonuclease activity at pH 4.5.

A recent conclusion that beef pancreas contained a molecular species of ribonuclease with intrinsically high activity at pH 4.5 has been found to be incorrect. The particular assay used in the earlier experiments gives anomalous results at acid pH in the presence of low concentrations of ions such as phosphate which was used during the fractionation. By turning to the more widely employed form of the perchloric acid precipitation assay, interference is avoided and the ribonuclease in beef pancreas is confirmed as consisting almost completely of the molecular species well-characterized as ribonuclease A. The clarification of the assay question permits a clear interpretation of the results of each step of the chromatographic purification procedure that led to the initial conclusion, including an artifact that arose when gel filtration was attempted with distilled water rather than with buffer.

Animals↗
PubMed1976

The concerted inactivation of Escherichia coli uridine diphosphate galactose 4-epimerase by sugar nucleotide together with a free sugar.

1. The combined effect of the sugar nucleotides UDP-D-fucose or UDP-D-glucuronic acid together with the free sugars D-fucose or L-arabinose is the inactivation of the Escherichia coli enzyme UDP-galactose 4-epimerase (EC 5.1.3.2). The sugar nucleotide or the free sugar alone or the sugar nucleotide plus 5'-Ump do not inactivate the enzyme. 2. The inactivation of the enzyme by its substrate UDP-D-glucose was not affected by the presence of free sugar. 3. In all cases the inactivation observed follows pseudo-first-order kinetics. 4. A comparison of various sugar nucleotides indicates that the hydroxymethyl group at position 6 of the sugar moiety of the natural substrates is important for substrate binding.

Arabinose↗
PubMed1976

Comparison of antitumor activities of pancreatic ribonuclease and its cross-linked dimer.

The cross-linked dimer of bovine pancreatic RNase (M.W. 28,000) is significantly more effective than the monomer in inhibiting tumor development in mice when administered i.p. 1 day after inoculation with sarcoma 180J ascites cells. Animals bearing solid tumors were not affected. In AKR/J mice with advanced leukemia, a single i.p. injection of 100 mug of the dimer led to about 50% reduction in the enlarged lymph nodes and the spleen at 24 hr. The half-life of the dimer in the bloodstream has been determined to be 10 min in rats and 6 min in mice, compared to values of 5 and 3.5 min, respectively, for the monomer. Analyses of the tissues of untreated leukemic mice for RNase and RNase inhibitors show that the tumor tissues are not deficient in RNase activity. Considerations of possible mechanisms of action of the dimer indicate that other basic proteins in this size range may merit examination as cytostatic agents toward transformed cells.

Animals↗
PubMed1975

The first enzyme of the gal operon in inducible and operator-constitutive strains of Escherichia coli. A comparison of the porperties and amino-terminal sequences of UDP galactose 4-epimerase.

1. UDPgalactose 4-epimerase, the product of the first structural gene of the gal operon in Escherichia coli K-12, has been purified from strain HfrH and from its gal operator-constitutive mutant, HfrH 81-2. 2. The two enzymes are purified by the same procedure, behaving identically throughout. They are identical in sedimentation coefficient, sioelectric point, electrophoretic mobility at pH 8.8 and amino-terminal sequence for the first 30 residues. 3. Slight but reporducible differences were observed between the amino acid compositions and peptide maps of the two proteins. These differences may indicate real differences in the primary sequences of the proteins, but if so they are unlikely to be due to the operator-constitutive mutation because of the identy of the sequences for the first 30 residues. 4. No evidence was found to indicate that the gal operator might overlap with the first structural gene.

Amino Acid Sequence↗
PubMedDate not supplied

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