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PubMed1990

Fermentation studies of the secretion of Serratia marcescens nuclease by Escherichia coli.

The secretion of a Serratia marcescens nuclease was followed by fermentation with Escherichia coli. A plasmid, p403-SD2, carrying a 1.3-kilobase-pair insert with a 0.4-kilobase-pair region upstream of the nuclease gene caused a growth-phase-regulated expression of nuclease in E. coli in the same way as that seen in S. marcescens. Deletion of the regulatory gene generating plasmid p403-Rsa1 resulted in a constitutive expression of the nuclease. Anaerobiosis stimulated the expression from p403-SD2 in stationary growth phase by a factor of 10 compared with expression stimulated by cultivation in aerobic conditions; no such effect was found for plasmid p403-Rsa1. Different nutritional factors caused the expression level and the amount of extracellular nuclease to vary more when nuclease was expressed from plasmid p403-SD2 than when it was expressed from plasmid p403-Rsa1. A correlation between the regulatory gene and the extracellular secretion of nuclease is proposed.

Bacteriological Techniques↗

PubMed1974

Surface-bound nuclease of Staphylococcus aureus: localization of the enzyme.

The cellular localization of staphylococcus nuclease, previously known as an exoenzyme, was investigated, and the following results were obtained. (i) When Staphylococcus aureus cells were converted to protoplasts by cell wall lytic enzyme L-11 (a bacteriolytic enzyme purified from Flavobacterium sp. which specifically hydrolyzes amide and peptide linkages of murein layers), over 80% of the cell-bound nuclease was released into the surrounding sucrose medium. (ii) The cell-bound nuclease was associated with the cell-wall membrane fraction of mechanically disrupted cells. (iii) The nuclease activity of cell-wall membrane fractions from cells during early and late stages of protoplast formation were compared. Less activity was found in the late stage. These results suggest that nuclease may be located at or near the surface of the cells. The distribution of cell-bound nuclease in the cell-wall membrane fraction varied with the growth conditions of S. aureus. The activity of alkaline phosphatase, another surface enzyme, was also investigated. Less of this enzyme than nuclease was released when the cells were converted to protoplasts.

Alkaline Phosphatase↗

PubMed1974

Surface-bound nuclease of Stapylococcus aureus: purification and properties of the enzymes.

The surface-bound nuclease of Staphylococcus aureus liberated during formation of protoplasts was purified 1,000-fold by chromatography on phosphocellulose. Its properties were compared with those of the known extracellular nuclease, purified 200-fold by the same procedures. The adsorbance of the surface-bound nuclease on phosphocellulose was distinctly different from that of the extracellular nuclease, but other properties of the two enzymes were similar. Both enzymes had a pH optimum of about 10 and required Ca(2+) for activity. Both enzymes hydrolyzed deoxyribonucleic acid (DNA) and ribonucleic acid, and denatured DNA was a better substrate than native DNA. Both enzymes were inhibited by the same metal ions. Nuclease-less mutants of S. aureus were isolated from S. aureus 209P by using N-methyl-N'-nitroso-N-nitrosoguanidine. These mutants contained neither surface-bound nor extracellular nuclease activity. These results suggest that the surface-bound and extracellular nucleases are expressed from the same cistron of S. aureus.

Ammonium Sulfate↗

PubMed1999

Cloning of mnuA, a membrane nuclease gene of Mycoplasma pulmonis, and analysis of its expression in Escherichia coli.

Membrane nucleases of mycoplasmas are believed to play important roles in growth and pathogenesis, although no clear evidence for their importance has yet been obtained. As a first step in defining the function of this unusual membrane activity, studies were undertaken to clone and analyze one of the membrane nuclease genes from Mycoplasma pulmonis. A novel screening strategy was used to identify a recombinant lambda phage expressing nuclease activity, and its cloned fragment was analyzed. Transposon mutagenesis was used to identify an open reading frame of 1,410 bp, which coded for nuclease activity in Escherichia coli. This gene coded for a 470-amino-acid polypeptide of 53,739 Da and was designated mnuA (for "membrane nuclease"). The MnuA protein contained a prolipoprotein signal peptidase II recognition sequence along with an extensive hydrophobic region near the amino terminus, suggesting that the protein may be lipid modified or that it is anchored in the membrane by this membrane-spanning region. Antisera raised against two MnuA peptide sequences identified an M. pulmonis membrane protein of approximately 42 kDa by immunoblotting, which corresponded to a trypsin-sensitive nucleolytic band of the same size. Maxicell experiments with E. coli confirmed that mnuA coded for a nuclease of unknown specificity. Hybridization studies showed that mnuA sequences are found in few Mycoplasma species, suggesting that mycoplasma membrane nucleases display significant sequence variation within the genus Mycoplasma.

Amino Acid Sequence↗

PubMed1975

Transfection of Escherichia coli spheroplasts. V. Activity of recBC nuclease in rec+ and rec minus spheroplasts measured with different forms of bacteriophage DNA.

The in vivo activity of the recBC nuclease was assayed by transfection of isogenic rec+ and rec minus spheroplasts with bacteriophage DNA of various origin and structure. The results indicate that the recBC nuclease can limit transfection at several stages during the production of an infective center; such limitations depend primarily on whether the DNA is in, or assumes, a nuclease-sensitive structure. The first stage of limitation can occur when a nuclease-sensitive transfecting molecule enters the spheroplast. Other potential limitation points occur during replication and maturation of the bacteriophage DNA. The initial stage can be bypassed by using recBC nuclease-resistant molecules such as circular forms. Through analysis of results with other DNA structures, we found that in vivo the effects of the double-strand exonucleolytic activity of the recBC nuclease predominated. The effects of the single-strand nuclease activities seem to be modified from those observed for the purified enzyme in vitro (Karu et al., 1974). Inside the cell, the single-strand exonuclease activity is very weak and the single-strand endonuclease activity is abolished almost completely.

Adenosine Triphosphatases↗

PubMed1982

Deletion mutants which affect the nuclease-sensitive site in simian virus 40 chromatin.

A short segment of simian virus 40 (SV40) chromatin on the late side of the origin of replication is hypersensitive to nuclease cleavage. The role of DNA sequence information in this nuclease-sensitive feature was examined by constructing deletion mutations in this region. Deletions were introduced into the inserted segment of in(Or)-1411 (a viable, partially duplicated variant of SV40), and nuclease sensitivity of the inserted segment was compared with that of the unaltered sequences in their normal location in the viral genome. Extended deletions (118 to 161 base pairs) essentially abolished nuclease sensitivity within the inserted segment. Shorter deletions (21 to 52 base pairs) at separate locations retained the nuclease-sensitive feature. In some short-deletion mutants nuclease susceptibility was substantially reduced. We conclude that more than one genetic element in this region contributes to the organization of the nuclease-sensitive feature and that the SV40 72-base repeat is not, in itself, sufficient signal for this feature.

Animals↗

PubMed1976

Single-strand nuclease action on heat-denatured spermiogenic chromatin.

The aim of this study was to compare the sensitivity of chromatin from representative cellular stages of spermiogenesis to a single-strandeded nuclease after heat denaturation. Thermal denaturation of chromatin was assayed in situ in fixed round, elongating and elongated spermatids and in testicular sperm from mice. Production of single-stranded deoxyribonucleic acid (DNA) at elevated temperatures was monitored by digesting chromatin with endonuclease specific for single-stranded DNA (S1 nuclease), staining the residual DNA with gallocyanin-chrome alum (GAC) and measuring the stain content by absorption cytophotometry. Changes in GCA staining were minimal over the temperature range of 22-90 degrees C in each cell type not exposed to nuclease. Staining of undigested cells decreased progressively with advancing cell maturity. Nuclease had no effect on the GCA content of round spermatids below 60 degrees C, but above this temperature there was a progressive decrease in GCA-stainable chromatin. Both round and elongating spermatid stages showed a significantly greater sensitivity to nuclease digestion than did more mature stages; sperm showed no effects of nuclease action below 80 degrees C. Progressive chromatin condensation and a concomitant decrease in the number of available DNA phosphate groups during spermiogenic cell maturation may be responsible for the observed decline in sensitivity to nuclease and decreased GCA staining. Thermal denaturation of round spermatids labeled with 3H-thymidine produced no change in autoradiographic mean nuclear grain counts, indicating no loss of thymidine-labeled DNA from the slides during denaturation. When round spermatids and sperm were hydrolyzed with hot tricholoroacetic acid before staining, both nuclear GCA content and autoradiograph grain count were partially reduced, indicating incomplete DNA removal. Almost complete loss of Feulgen-stainable material occurred in these cells and may be due to depurination and elimination of Feulgren-reactant aldehyde groups.

Animals↗

PubMed1999

Barley aleurone cell death is not apoptotic: characterization of nuclease activities and DNA degradation

Barley aleurone cells undergo programmed cell death (PCD) when exposed to gibberellic acid (GA), but incubation in abscisic acid (ABA) prevents PCD. We tested the hypothesis that PCD in aleurone cells occurs by apoptosis, and show that the hallmarks of apoptosis, namely DNA cleavage into 180 bp fragments, plasma membrane blebbing, and the formation of apoptotic bodies do not occur when aleurone cells die. We show that endogenous barley aleurone nucleases and nucleases present in enzymes used for protoplast preparation degrade aleurone DNA and that DNA degradation by these nucleases is rapid and can result in the formation of 180 bp DNA ladders. Methods are described that prevent DNA degradation during isolation from aleurone layers or protoplasts. Barley aleurone cells contain three nucleases whose activities are regulated by GA and ABA. GA induction and ABA repression of nuclease activities correlate with PCD in aleurone cells. Cells incubated in ABA remain alive and do not degrade their DNA, but living aleurone cells treated with GA accumulate nucleases and hydrolyze their nuclear DNA. We propose that barley nucleases play a role in DNA cleavage during aleurone PCD.

Journal Article↗

PubMed1999

Barley aleurone cell death is not apoptotic: characterization of nuclease activities and DNA degradation.

Barley aleurone cells undergo programmed cell death (PCD) when exposed to gibberellic acid (GA), but incubation in abscisic acid (ABA) prevent PCD. We tested the hypothesis that PCD in aleurone cells occurs by apoptosis, and show that the hallmark of apoptosis, namely DNA cleavage into 180 bp fragments, plasma membrane blebbing, and the formation of apoptotic bodies do not occur when aleurone cells die. We show that endogenous barley aleurone nucleases and nucleases present in enzymes used for protoplast preparation degrade aleurone DNA and that DNA degradation by these nucleases is rapid and can result in the formation of 180 bp DNA ladders. Methods are described that prevent DNA degradation during isolation from aleurone layers or protoplasts. Barley aleurone cells contain three nucleases whose activities are regulated by GA and ABA. CA induction and ABA repression of nuclease activities correlate with PCD in aleurone cells. Cells incubated in ABA remain alive and do not degrade their DNA, but living aleurone cells treated with GA accumulate nucleases and hydrolyze their nuclear DNA. We propose that barley nucleases play a role in DNA cleavage during aleurone PCD.

Abscisic Acid↗

PubMed2000

Cloning and characterization of a novel nuclease from shrimp hepatopancreas, and prediction of its active site.

Approximately 95% of the amino acid sequence of a shrimp (Penaeus japonicus) nuclease was derived from protease-digested peptides. A 1461-base cDNA for the nuclease was amplified and sequenced with degenerate primers based on the amino acid sequence and then specific primers by 3' and 5' RACE (rapid amplification of cDNA ends). It contains an open reading frame encoding a putative 21-residue signal peptide and a 381-residue mature protein. The N-terminus of the enzyme is pyroglutamate, deduced from composition and matrix-assisted laser desorption ionization-time-of-flight MS analyses, and confirmed by a glutamine residue in the cDNA sequence. The enzyme has 11 Cys residues, forming five intramolecular disulphides. The eleventh Cys residue was linked to a thiol compound with an estimated molecular mass of between 500 and 700 Da. A sequence similarity search revealed no homologous proteins but residues 205-255 shared a conserved active-site motif within a distinct group of nucleases. His(211) in this conserved motif was shown to be very important in catalysis by site-specific modification with (14)C-labelled iodoacetate. The shrimp nuclease, previously designated DNase I, does indeed possess a low level of hydrolytic activity towards RNA in the presence of Mg(2+) and Ca(2+). The conservation of functionally important residues during distant evolution might imply that the catalytic mechanisms are similar in these nucleases, which should be classified in one subfamily. Finally, an active-site structure for shrimp nuclease was proposed on the basis of published structural data and the results of mutational and biochemical analyses of Serratia nuclease.

Amino Acid Sequence↗

PubMed1989

Enzymatic analysis of isomeric trithymidylates containing ultraviolet light-induced cyclobutane pyrimidine dimers. I. Nuclease P1-mediated hydrolysis of the intradimer phosphodiester linkage.

Our recent findings suggest that enzymatic hydrolysis of the intradimer phosphodiester bond may constitute the initial step in the repair of UV light-induced cyclobutane pyrimidine dimers in human cells. To examine the susceptibility of this phosphodiester linkage to enzyme-mediated hydrolysis, the trinucleotide d-Tp-TpT was UV-irradiated and the two isomeric compounds containing a cis-syn-cyclobutane dimer were isolated by high performance liquid chromatography and treated with various deoxyribonucleases. Snake venom phosphodiesterase hydrolyzed only the 3'-phosphodiester group in the 5'-isomer (d-T less than p greater than TpT) but was totally inactive toward the 3'-isomer (d-TpT less than p greater than T). In contrast, calf spleen phosphodiesterase only operated on the 3'-isomer by cleaving the 5'-internucleotide bond. Kinetic analysis revealed that (i) the activity of snake venom phosphodiesterase was unaffected by a dimer 5' to a phosphodiester linkage, (ii) the action of calf spleen phosphodiesterase was partially inhibited by a dimer 3' to a phosphodiester bond, and (iii) Escherichia coli phr B-encoded DNA photolyase reacted twice as fast with d-T less than p greater than TpT as with d-TpT less than p greater than T. Mung bean nuclease, nuclease S1, and nuclease P1 all cleaved the 5'-internucleotide linkage, but not the intradimer phosphodiester bond, in d-TpT less than p greater than T. Both phosphate groups in d-T less than p greater than TpT were refractory to mung bean nuclease or nuclease S1. Incubation of d-T less than p greater than TpT with nuclease P1, however, generated the novel compound dT less than greater than d-pTpT containing a severed intradimer phosphodiester linkage. Accordingly, nuclease P1 represents the first purified enzyme known to hydrolyze an intradimer phosphodiester linkage.

Chromatography, DEAE-Cellulose↗

PubMed1993

Characterization of natural and recombinant nuclease isoforms by electrospray mass spectrometry.

Isoforms of natural and recombinant nuclease have been characterized on the basis of their M(r) as determined by electrospray m.s.. The natural nuclease was isolated and purified from Serratia marcescens B10M1 and the recombinant nuclease from Escherichia coli MT102 carrying the plasmid p403-SD2. The primary structure of each of the isoforms isolated from the nuclease preparations was established by comparing their mass with the known amino acid sequence derived from the nucleotide sequence of the nuc gene. All the preparations were found to be contaminated with the same N-terminal split variants of native nuclease, although the natural nuclease contained much larger amounts of these isoforms than did the recombinant nuclease. The structure of some of the isoforms could be verified by N-terminal sequencing, and nearly all of them by isoelectric focusing.

Endodeoxyribonucleases↗

PubMed1984

A close association between sites of DNase I hypersensitivity and sites of enhanced cleavage by micrococcal nuclease in the 5'-flanking region of the actively transcribed ovalbumin gene.

The organization of chromatin was analysed in a segment of the chicken ovalbumin gene extending 6.5 kb upstream from the start site of transcription. Nuclei of chicken oviduct cells and of erythrocytes, and preparations of 'naked' DNA were digested with DNase I and with micrococcal nuclease. The locations of specific nuclease cleavage sites were determined by analyzing the fragments obtained with an indirect end-labeling technique. In oviduct nuclei there are four regions of DNase I hypersensitivity centered at approximately 0.15, 0.80, 3.2 and 6.0 kb upstream from the mRNA cap site. DNase I hypersensitive regions are absent from the 5'-flanking regions of erythrocyte nuclei. Micrococcal nuclease cleavage sites were found that are unique to oviduct nuclei and others that are enhanced in oviduct nuclei, relative to erythrocyte nuclei and to naked DNA. The locations of these micrococcal nuclease cleavage sites are closely associated with the DNase I hypersensitive regions. Nuclease hypersensitivity in the 5'-flanking region of oviduct nuclei reflects alterations in chromatin structure that are specifically correlated with gene expression. Our results suggest the presence at hypersensitive regions of specific proteins which alter the chromatin structure, making the DNA more accessible to nuclease attack.

Animals↗

PubMed1995

Interactions in nonnative and truncated forms of staphylococcal nuclease as indicated by mutational free energy changes.

Several mixed disulfide variants of staphylococcal nuclease have been produced by disulfide bond formation between nuclease V23C and methane, ethane, 1-propane, 1-n-butane, and 1-n-pentane thiols. Although CD spectroscopy shows that the native state is largely unperturbed, the stability toward urea-induced unfolding is highly dependent on the nature of the group at this position, with the methyl disulfide protein being the most stable. The variant produced by modification with iodoacetic acid, however, gives a CD spectrum indicative of an unfolded polypeptide. Thiol-disulfide exchange equilibrium constants between nuclease V23C and 2-hydroxyethyl disulfide have been measured as a function of urea concentration. Because thiol-disulfide exchange and unfolding are thermodynamically linked, the effects of a mutation (disulfide exchange) can be partitioned between various conformational states. In the case of unmodified V23C and the 2-hydroxyethyl protein mixed disulfide, significant effects in the nonnative states of nuclease are observed. Truncated forms of staphylococcal nuclease are thought to be partially folded and may be good models for early folding intermediates. We have characterized a truncated form of nuclease comprised of residues 1-135 with a V23C mutation after chemical modification of the cysteine residue. High-resolution size-exclusion chromatography indicates that modification brings about significant changes in the Stokes radius of the protein, and CD spectroscopy indicates considerable differences in the amount of secondary structure present. Measurement of the disulfide exchange equilibrium constant between this truncated protein and 2-hydroxyethyl disulfide indicate significant interactions between position 23 and the rest of the protein when the urea concentration is lower than 1.5 M.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical Phenomena↗

PubMed1997

Biosynthetic incorporation of tryptophan analogues into staphylococcal nuclease: effect of 5-hydroxytryptophan and 7-azatryptophan on structure and stability.

5-Hydroxytryptophan (5HW) and 7-azatryptophan (7AW) are analogue of tryptophan that potentially can be incorporated biosynthetically into proteins and used as spectroscopic probes for studying protein-DNA and protein-protein complexes. The utility of these probes will depend on the extent to which they can be incorporated and the demonstration that they cause minimal perturbation of a protein's structure and stability. To investigate these factors in a model protein, we have incorporated 5HW and 7AW biosynthetically into staphylococcal nuclease A, using a trp auxotroph Escherichia coli expression system containing the temperature-sensitive lambda cI repressor, Both tryptophan analogues are incorporated into the protein with good efficiency. From analysis of absorption spectra, we estimate approximately 95% incorporation of 5HW into position 140 of nuclease, and we estimate approximately 98% incorporation of 7AW, CD spectra of the nuclease variants are similar to that of the tryptophan-containing protein, indicating that the degree of secondary structure is not changed by the tryptophan analogues. Steady-state fluorescence data show emission maxima of 338 nm for 5HW-containing nuclease and 355 nm for 7AW-containing nuclease. Time-resolved fluorescence intensity and anisotropy measurements indicate that the incorporated 5HW residue, like tryptophan at position 140, has a dominant rotational correlation time that is approximately the value expected for global rotation of the protein. Guanidine-hydrochloride-induced unfolding studies show the unfolding transition to be two-state for 5HW-containing protein, with a free energy change for unfolding that is equal to that of the tryptophan-containing protein. In contrast, the guanidine-hydrochloride-induced unfolding of 7AW-containing nuclease appears to show a non-two-state transition, with the apparent stability of the protein being less than that of the tryptophan form.

5-Hydroxytryptophan↗

PubMed1982

Responses to androgens of rat ventral prostate nuclear androgen-binding sites sensitive and resistant to micrococcal nuclease.

Rat ventral prostate nuclei were separated into three major fractions by mild digestion with micrococcal nuclease and two fractions by extensive digestion. All fractions contained androgen-binding sites. Almost 50% of nuclear binding sites were resistant to enzymic digestion when only 5-15% of total DNA was resistant. Under milder digestion conditions, 21% of nuclear binding sites were associated with an intermediate fraction, representing 16% of total nuclear DNA, which was enriched in specific androgen-regulated gene sequences. This fraction was rapidly degraded by more extensive digestion. The nuclease sensitivity of these particular genes was markedly influenced by castration and the administration of dihydrotestosterone to castrated animals. The nuclear content of both nuclease-resistant and -sensitive androgen-binding sites was decreased by castration. Whereas the administration of androgen to animals castrated 1 day previously preferentially replenished nuclease-resistant sites, nuclease-sensitive sites, including those associated with transcriptionally active regions, had apparent priority when androgen was supplied to animals castrated 7 days previously. The significance of these observations to the regulation of nuclear processes and the possible interrelationships of nuclease-sensitive and -insensitive sites are discussed.

Animals↗

PubMed1994

Magnetic resonance studies of the binding of oligonucleotide substrates to mutants of staphylococcal nuclease.

By a combination of NMR docking and model building, the substrate binding site on staphylococcal nuclease was found to accommodate a trinucleotide and to consist of three subsites, each interacting with a single nucleotidyl unit of DNA. Binding of the essential Ca2+ activator and substrate cleavage occur between subsites 1 and 2. Hence, catalytically productive binding would span subsites 1 and 2 while nonproductive binding would span subsites 2 and 3. Lys-49 is near subsite 1, and Lys-84 and Tyr-115 interact with substrates at subsite 3 [Weber, D.J., Gittis, A.G., Mullen, G.P., Abeygunawardana, C., Lattman, E.E., Mildvan, A.S. Proteins 13:275-287, 1992]. The proposed locations of these subsites were independently tested by the effects of the K49A, K84A, and Y115A mutations of staphylococcal nuclease on the binding of Mn2+, Ca2+, and the dinucleotide and trinucleotide substrates, 5'-pdTdA, dTdA, and dTdAdG. These three mutants have previously been shown to be fully active and to have CD and 2D NMR spectra very similar to those of the wild-type enzyme (Chuang, W.-J., Weber, D.J., Gittis, A.G., Mildvan, A.S. Proteins 17:36-48, 1993). All three mutant enzymes and their pdTdA and dTdA complexes (but not their dTdAdG complex) bind Mn2+ and Ca2+ more weakly than the wild-type enzyme by factors ranging from 2 to 11. The presence of a terminal phosphate as in 5'-pdTdA raises the affinity of the substrate for staphylococcal nuclease and its three mutants by two orders of magnitude and for the corresponding enzyme-metal complexes by three to four orders of magnitude, suggesting that the terminal phosphate is coordinated by the enzyme-bound divalent cation. Such complexation would result in the nonproductive binding of 5'-pdTdA at subsites 2 and 3. Accordingly, the K84A and Y115A mutations significantly weaken the binding of 5'-pdTdA and its metal to staphylococcal nuclease by factors of 2.2 to 37.8, while the K49A mutation has much smaller or no effect. Such nonproductive binding explains the low activity of staphylococcal nuclease with small substrates, especially those with a terminal phosphate. Similarly, the K84A and Y115A mutations weaken the binding of dTdA and its metal complexes to the enzyme by factors of 3.4 to 13.1 while the K49A mutation has smaller effects indicating significant nonproductive binding of dTdA. The trinucleotide dTdAdG binds more tightly to wild-type and mutant staphylococcal nuclease and to its metal complexes than does the dinucleotide dTdA by factors of 2.4 to 12.2, reflecting the occupancy of an additional subsite.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium↗

PubMed1975

The action of staphylococcal nuclease (EC-number 3. 1. 4. 7.) on thymus nucleohistone (TNH) and on some nucleoprotamines.

The biphasic nature of the time course of the action of staphylococcal nuclease on thymus nucleohistone was confirmed by studying the hydrolysis of this nucleoprotein at various enzyme concentrations. The transition from the rapid first to the sluggish second phase of the time course was particularly distinct at the highest enzyme concentrations. The rapid initial phase of the hydrolysis curve leveled off sharply when between 60 and 65 per cent of the total TNH phosphorus had been converted to acid-soluble phosphorus compounds. The insoluble complexes of TNH with protamines were found to be very resistant against the action of staphylococcal nuclease. The time course of the action of staphylococcal nuclease on a commercial nucleoprotamine of salmon testicles was found to become very sluggish when between 35 and 40 per cent of its total phosphorus had been converted to acid-soluble phosphorus compounds. When nucleoprotamines prepared in the laboratory from the secreted sperm cell suspension of Brown Brook Trout were digested with staphylococcal nuclease, only between 15 and 20 per cent of the total phosphorus were cleaved to acid-soluble phosphorus compounds during the rapid phase of the nuclease action. The respective values for the phosphorus fractions available for magnesium-binding and those susceptible to the rapid cleavage by staphylococcal nuclease were found to be very similar.

Animals↗