Mouse DNA polymerase alpha. Subunit structure and identification of a species with associated exonuclease

Two species of alpha-polymerase with very similar catalytic properties have been purified to near homogeneity from a soluble protein fraction of mouse myeloma. Sedimentation analysis in 0.5 M salt-containing glycerol gradients indicated that both species had a native Mr of about 190,000. Each species contained nonidentical subunits with apparent molecular weights of about 47,000 and 54,000. Subunits of Mr = approximately 50,000 had been found previously in calf thymus alpha-polymerase (Holmes, A. M., Hesslewood, I. P., and Johnston, I. R. (1974) Eur. J. Biochem. 43, 487-499; (1976) Eur. J. Biochem. 62, 229-235). Tryptic peptide mapping failed to reveal primary structure homology between the subunits of the two enzymes. Thus, the two alpha-polymerases are clearly different species. These two enzymes are further distinguished by the fact that one of them has associated exonuclease activities. One activity degraded single-stranded DNA to mononucleotides in the 3' leads to 5' direction and acted distributively. The other exonuclease activity also degraded single-stranded DNA to mononucleotides, but this degradation was in the 5' leads to 3' direction in a processive fashion. Both exonuclease activities co-migrated with the polymerase activity during the final purification step of polyacrylamide gradient gel electrophoresis, which yielded the essentially homogenous alpha-polymerase, and also during sedimentation of the purified enzyme through a high salt glycerol gradient.

Arthroscopy of the wrist and finger joints

Ninety arthroscopies of the wrist and finger joints in 34 clinical cases and two amputated arms were carried out with the number 24 arthroscope. Eighty-four wrist and finger joints of four cadavers and two amputated arms were also dissected for macroscopic observation. Most portions of the interior structures of the wrist and finger joints can be observed by the dorsal approaches. Color photography and punch biopsy are also possible. Some arthroscopic photographs taken with the number 24 arthroscope are illustrated. From these experiences it is concluded that the number 24 arthroscope is a useful diagnostic tool in arthroscopy of the small joints, even though there are still many problems.

Purification and characterization of the anticoagulant principle of Trimeresurus mucrosquamatus venom

By means of CM-Sephadex column chromatography, Trimeresurus mucrosquamatus venom was separated into 20 fractions. Fraction XX had the marked anticoagulant action. This fraction was refractionated three times on Sephadex G-75, and a single peak was obtained. The patterns of microzone and disc electrophoresis also showed a single band. A single, symmetrical boundary with a value of 1.61 S was obtained by ultracentrifugation. It was a single peptide chain with a molecular weight of 11 700. The isoelectric point was higher than pH 10. The anticoagulant principle possessed phospholipase A activity and was calcium ion dependent. It did not possess proteolytic, tosyl-L-arginine methyl ester esterase, phosphodiesterase and alkaline phosphomonoesterase activities of the crude venom. The phospholipase A activity was heat-labile at pH 7.4, but was heat-stable at pH 5.6. The anticoagulant activity was more resistant to heat treatment as compared with phospholipase A activity. The anitoagulant action of the purified principle was competitively inhibited by platelet phospholid, tissue thromboplastin and cephalin, and was neutralized by antiserum. The anticoagulant principle inhibited platelet aggregation induced by ADP. It did not destroy fibrinogen, Factor X, prothrombin and thrombin; nor did it induce fibrinolysis nor interfere with the interaction between thrombin and fibrinogen. It is concluded that the anticoagulant action of this phospholipase A was due to the inhibition of the activations of Factors X and II through the inactivation of the procoagulant activity of phospholipids mediated partly by phospholipid-binding activity of this venom enzyme and partly by its enzymatic hydrolysis of phospholipids.

Polynucleotide recognition by DNA alpha-polymerase

In a survey of template-primer preference of a mouse myeloma DNA alpha-polymerase, the fastest rate of DNA synthesis was with poly(dT) as template and (rA)24 as primer. Such a preference for poly(dT).oligo(rA) was not observed with other DNA polymerases of mouse origin. DNA synthesis in this system resulted in formation of oligo(dA) chains, not template-length poly(dA); thus, the average enzyme molecule bound to a poly(dT).(rA)24 complex and initiated a new oligo(dA) chain many times during the incubation. Binding experiments revealed that the alpha-polymerase had high affinity for poly(dT). Although the alpha-polymerase did not bind to poly(dl) and failed to replicate it inreactions with a base pair complementary primer, poly(dl) was replicated after a (dT) block had been grafted to its 3'-end and the oligo(rA) primer had been added. In similar experiments, the (dT) block was found to be much more effective than other 3'-terminal blocks in promoting replication of denatured calf thymus DNA. The results indicate that specific base sequences may regulate initiation of DNA syntehsis by this alpha-polymerase.

Properties of mammalian cells transformed by temperature-sensitive mutants of avian sarcoma virus

Fibroblasts from European field vole (Microtus agrestis) and from normal rat kidney (NRK) have been infected by avian sarcoma virus mutants which are temperature-sensitive for the maintenance of transformation. These cells are transformed at 33 degrees C, but show normal cell characteristics in morphology, colony formation in agar, saturation density, sugar uptake and membrane proteins at 39 degrees C and 40 degrees C, the nonpermissive temperatures. Ts mutant virus was rescued from most of the ts transformed cell lines. NRK cells infected by avian sarcoma virus ts mutants and kept at the nonpermissive temperature can be transformed by wild-type avian sarcoma virus. The susceptibility of the temperature-sensitive NRK lines to this transformation is higher than the susceptibility of uninfected NRK at either permissive or nonpermissive temperature.

Physicochemical properties of alpha- and beta-fibrinogenases of Trimeresurus mucrosquamatus venom

alpha- and beta-Fibrinogenases (EC 3.4.21.5) were purified from Trimeresurus mucrosquamatus venom by the technique of recycling chromatography. Both enzymes were single polypeptide chains and homogeneous as judged by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis and ultracentrifugation. The sedimentation constants of alpha- and beta-fibrinogenases were 2.52 and 3.04 respectively. The molecular weight of alpha-fibrinogenase was 21 500--23 400, and that of beta-fibrinogenase was 25 000--26 000. The contents of proline, glycine and tryptophan were higher in beta-fibrinogenase than in alpha-fibrinogenase. The isoelectric points of alpha- and beta-fibrinogenases were pH 8.1 and 5.7 respectively. The optimal pH of alpha-fibrinogenase was about 7.4 and that of beta-fibrinogenase was around 8.5. The activity of alpha-fibrinogenase was completely destroyed after 30 min at 60 degrees C, pH 5.6, 7.4 and 9.0, while that of beta-fibrinogenase was not significantly affected by the same treatment. Both enzymes showed proteolytic activities toward fibrinogen and casein, but were devoid of phospholipase A, alkaline phosphomonoesterase and phosphodiesterase activities of the crude venom. The tosyl-L-arginine methylester esterase activity of beta-fibrinogenase was about 17 times that of the crude venom, while alpha-fibrinogenase was completely devoid of this activity. The fibrinogenolytic activity of alpha-fibrinogenase was markedly inhibited by EDTA and cysteine, while that of beta-fibrinogenase was inhibited markedly by phenylmethane sulfonylfluoride and slightly by tosyl-L-lysine chloromethylketone and cysteine.

Actinomycin D-deoxynucleotide complexes as models for the actinomycin D-DNA complex. The use of nuclear magnetic resonance to determine the stoichiometry and the geometry of the complexes

The use of proton and carbon-13 magnetic resonance spectroscopy for the determination of the geometry and the stoichiometry of the actinomycin D-deoxyguanosine 5'-monophosphate complex is outlined. The dimerization of actinomycin D has been reexamined by recording the proton magnetic resonance spectrum of actinomycin D to much lower concentrations through the use of Fourier transform nuclear magnetic resonance techniques. The effect of the actinomycin D dimerization on the observed chemical shifts that results from the additon of nucleotides to an actinomycin D solution is directly demonstrated by comparing the actinomycin D-nucleotide titrations at both low (approximately 0.3 mM) and high (approximately 12 mM) concentrations of actinomycin D. In the presence of excess nucleotide the chemical shifts of the actinomycin D groups were essentially the same for both the low and high concentration titrations. The complexes of actinomycin D with pdG-dC, dG-dC, deoxyguanosine 3'-monophosphate, G-C, C-G, dIMP(5'), 2, 6-diaminopurine deoxyribose, and other nucleotides were also investigated by proton magnetic resonance and visible spectral titrations. These data were interpreted in terms of the molecular geometry of the complexes and in terms of the effect of the structure of the nucleotide base on the relative binding affinity of the nucleotides for the two nucleotide binding sites of actinomycin D. The carbon-13 chemical shifts of dGMP(5') were measured as a function of concentration over the concentration range of 0.5-0.025 M. The infinite dilution carbon-13 chemical shifts were graphically estimated from the dilution curves. These values were used to calculate the changes in the chemical shifts of the dGMP carbons that result from the formation of an actinomycin D-(dGMP)2 complex. It was not possible to interpret these carbon-13 chemical shift changes in terms of only ring current effects, which thus rules out the use of carbon-13 spectroscopy in the determination of the geometries of the actinomycin D complexes with the mono- and dinucleotides. The induced chemical shifts in the proton spectra may be used in the determination of the geometries of the complexes. A consideration of these data for the above nucleotide series shows that the predominant complex formed is one in which the guanine rings in the two nucleotide binding sites of actinomycin D are oriented in a manner very similar to that observed in the cocrystalline complex of actinomycin D with deoxyguanosine.

Protein synthesis in rabbit reticulocytes. A study of Met-tRNA f Met binding factor(s) and Met-tRNA f Met binding to ribosomes and AUG codon

The effects of additions of Mg-2+, ribosomes, and AUG codon on the Met-tRNAf Met-initiation factor-GTP complex were studied using a Millipore filtration method (J. Biol. Chem. 248, 4500 (1973)). Upon addition of increasing concentration of Mg-2+, the Met-tRNAf Met-initiation factor-GTP complex dissociates into free Met-tRNAf Met and initiation factor (GTP), with an infection around 1.5 to 2 mM Mg-2+. The Mg-2+-induced dissociation of Met-tRNAf Met-initiation factor-GTP complex was enhanced at ice bath temperature. At 37 degrees and in the presence of 1.5 to 2mM Mg-2+, the Met-tRNAf Met-initiation factor-GTP complex catalyzes the transfer of Met-tRNAf Met to ribosomes and AUG codon. Ribosome bound Met-tRNAf Met is stable to Mg-2+ and low temperature. A Millipore filtration assay for studies of (35S)Met-tRNAf Met binding to ribosomes and Aug codon has been developed. The assay procedure is carried out in three stages. In Stage I, the Met-tRNAf Met is bound to initiation factor in the presence of GTP, AUG codon (required for Stage II reaction), and 3.7 times 10-5 M aurintricarboxylic acid. The incubation is carried out at 37 degrees for 5 min. In Stage II, ribosomes and Mg-2+ (1.5 to 2mM final concentration) are added and the incubation is continued at 37 degrees for 10 min. In Stage III, more Mg-2+ is added to make the final Mg-2+ concentration of the incubation mixture 5 mM, and the reactions are further incubated at ice bath temperature for 10 min. The reactions are then terminated by addition of excess cold wash buffer and filtered through Millipore filters. Under the standard assay conditions, the radioactivity bound to Millipore filters in the absence of ribosomes and AUG codon is markedly reduced. Addition of ribosomes alone gave a significant increase in the radioactivity bound to Millipore filters. A further 2- to 3-fold stimulation of binding of (35S)Met-tRNAf Met to Millipore filters was observed when both ribosomes and AUG codon were added. The Met-tRNAf Met bound to ribosomes under the assay condition was reactive with puromycin. Upon DEAE-cellulose chromatography of a partially purified mixture of initiation factors (IF), Met-tRNAf Met binding activities separate into two forms, and are designated as IF-1A and IF-1B. These two forms can be distinguished by the stabilities of their respective Met-tRNAf Met-IF-1-GTP complexes to Mg-2+. The Met-tRNAf Met-IF-1A-GTP complex is distinctly more stable in the presence of Mg-2+ than Met-tRNAf Met-IF-1B-GTP complex. Continue.

Correlation of head circumference and crown-rump length in newborn infants. A potential indicator of congenital maldevelopment

A study of 305 consecutive neonatal autopsies done by two prosectors showed a high correlation between the head circumference (HC) and crown-rump length (CR). The calculated formula can be stated approximately as HC equals 0.9 CR + 2.5 cm, and the two measurements are for all practical purposes equal in the immediate neonatal period, regardless of race, sex, age and body weight. When the HC was found to be significantly larger than CR, hydrocephalus and certain types of chondrodystrophy were present. When the HC was significantly smaller than CR, there was a higher incidence of congenital heart disease, especially hypoplastic left heart syndrome, and congenital central nervous system disorders other than hydrocephalus. From a practical point of view, a significant difference is a discrepancy of more than 2.5 cm. 102 consecutive living neonates were also similarly studied. It appears that the CR length when carefully measured under standardized condition is more reliable than the crown-heel length.

Aeration of medical plastics

Because the metabolic reaction that gives ethylene oxide is sterilizing qualities also takes place with human protein, it is imperative that any residual gas be removed before the sterilized material is used on the patient. This paper presents a method of estimating aeration time required following sterilization of polyvinyl choride (PVC) to reduced toxic residues to a desired level. The method proposed involves calculation of the coefficient of diffusivity, and the use of a simplified diffusion equation to estimate aeration time.