Isolation and properties of extracellular proteinases from Sporothrix schenckii.

Sporothrix schenckii, mainly in the yeast form of the organism, produced extracellular proteinases when cultivated in liquid media containing albumin or collagen as a nitrogen source, but did not do so in brain heart infusion medium. Isolation of two extracellular proteinases from albumin-containing medium was performed by chromatography on DEAE-Sepharose CL-6B and Sephacryl S-200. Proteinase I had a molecular weight of 36,500, an optimal pH at 6.0, and a pI at 4.8. Despite its activities in weakly acidic conditions, proteinase I demonstrated chymotrypsinlike characteristics, these being indicated by strong inhibitory activity by phenylmethylsulfonyl fluoride and chymostatin and good kinetic constants for a synthetic chymotrypsin substrate, Suc-Ala-Ala-Pro-Phe-MCA. Proteinase II had a molecular weight of 39,000, an optimal pH at 3.5, and a pI at 3.8. Proteinase II showed cathepsin D-like characteristics, these being indicated by strong inhibitory activity by pepstatin, an acidic optimal pH, and good kinetic constants for hemoglobin. These two enzymes hydrolyzed natural substrates such as stratum corneum, type I collagen, and elastin although not type IV collagen. Proteinase production and cell growth in collagen-containing medium and the enzymatic digestion of skin constituents by isolated proteinases suggested that these two proteinases cooperatively enable the organism to invade skin and to obtain peptides from insoluble proteins.     

DNA strand breaks in mammalian tissues induced by methylarsenics

DNA damage induced by administration of dimethylarsinic acid (DMAA) to rats and mice was investigated. At 12 h after administration of DMAA, DNA single-strand breaks were induced markedly in lung. The majority of dimethylarsine, one of the main metabolites, in the expired air was excreted within 6–18 h after administration of DMAA to rats. In vitro experiments using nuclei isolated from lung of mice indicated that DNA strand breaks were caused by dimethylarsine. Furthermore, the strand breaks after exposure to dimethylarsine were reduced in the presence of catalase and/or superoxide dismutase. These results strongly suggest that the strand breaks are induced not by dimethylarsine itself but by active oxygen, e.g., O ₂ ^? and ·OH, produced both by dimethylarsine and molecular oxygen. When DNA was exposed to dimethylarsine, thiobarbituric acid (TBA)-reactive intermediates andcis-thymine glycol were produced. Dimethylarsine appears to induce DNA damage by the mechanism similar to the damage produced by ionizing radiation.     

Hormone-Autonomous Suspension Culture from Leaf Explants of Sugar Beets in Liquid Medium

Hormone autonomous callus was institutioniated reproduciblyon MS agar medium with 0.25 mg/liter of BA as the sole planthormone (AI medium) from young leaf explants of sugar beets.When leaf explants were inoculated into AI medium and culturedon a reciprocal shaker, single cells began to be released fromthe cut surfaces of the leaf pieces after 6 days, followed byactive release. When the single cells which had been releasedwere transferred to fresh liquid MS medium without any planthormones, they could divide and grow autonomously, giving riseto hormone-autonomous suspension cultures. The effects of BAon induction of hormone-autonomous cells are discussed. (Received March 12, 1987; Accepted October 13, 1987)     

Coordination structures and reactivities of compound II in iron and manganese horseradish peroxidases. A resonance Raman study

Resonance Raman investigations on compound II of native, diacetyldeuteroheme-, and manganese-substituted horseradish peroxidase (isozyme C) revealed that the metal-oxygen linkage in the compound differed from one another in its bond strength and/or structure. Fe(IV) = O stretching frequency for compound II of native enzyme was pH sensitive, giving the Raman line at 772 and 789 cm-1 at pH 7 and 10, respectively. The results confirmed the presence of a hydrogen bond between the oxo-ligand and a nearby amino acid residue (Sitter, A. J., Reczek, C. M., and Terner, J. (1985) J. Biol. Chem. 260, 7515-7522). The Fe(IV) = O stretch for compound II of diacetylheme-enzyme was located at 781 cm-1 at pH 7 which was 9 cm-1 higher than that of native enzyme compound II. At pH 10, however, the Fe(IV) = O stretch was found at 790 cm-1, essentially the same frequency as that of native enzyme compound II. The pK value for the pH transition, 8.5, was also the same as that of native compound II. Unlike in native enzyme, D2O-H2O exchange did not cause a shift of the Fe(IV) = O frequency of diacetylheme-enzyme. Thus, the metal-oxygen bond at pH 7 was stronger in diacetylheme-enzyme due to a weaker hydrogen bonding to the oxo-ligand, while the Fe(IV) = O bond strength became essentially the same between both enzymes at alkaline pH upon disruption of the hydrogen bond. A much lower reactivity of the diacetylheme-enzyme compound II was accounted to be due to the weaker hydrogen bond. Compound II of manganese-substituted enzyme exhibited Mn(IV)-oxygen stretch about 630 cm-1, which was pH insensitive but down-shifted by 18 cm-1 upon the D2O-H2O exchange. The finding indicates that its structure is in Mn(IV)-OH, where the proton is exchangeable with a water proton. These results establish that the structure of native enzyme compound II is Fe(IV) = O but not Fe(IV)-OH.     

Resonance Raman study of cytochrome b562-o complex, a terminal oxidase of Escherichia coli in its ferric, ferrous, and CO-ligated states

Cytochrome b562-o complex, a terminal oxidase in the respiratory chain of aerobically grown Escherichia coli, has been studied by resonance Raman spectroscopy in its air-oxidized, dithionite-reduced, and reduced and CO-ligated states. In the reduced state, with a 406.7-nm excitation, there appeared 1494 and 1473 cm-1 lines, indicating that low spin and high spin components are included in the cytochrome b562-o complex. For the air-oxidized protein, resonance Raman lines were observed at 1372, 1503, and 1580 cm-1 with a 413.1-nm excitation, indicating that there is a ferric low spin heme. In addition, a weak but appreciable Raman line was observed at 1480 cm-1 assignable to a ferric high spin heme. Accordingly, it was concluded that low spin and high spin components are included in the cytochrome b562-o complex in the reduced and the air-oxidized states. In the CO-ligated state, with a defocused laser beam of 413.1 nm, two Raman bands assignable to the Fe-CO stretching mode have been observed at 489 and 523 cm-1, as a major and a minor component, respectively. When the laser beam was focused upon the sample to cause a photodissociation of CO from the heme moiety, the intensity of the major band at 489 cm-1 was reduced as expected. On the other hand, the minor band at 523 cm-1 remained still obvious. It was suggested that the cytochrome b562-o complex may have an additional anomalous site for CO that is resistant to photodissociation.     

Cloning of the Escherichia coli gene for the stringent starvation protein

Summary In order to clone the Escherichia coli gene for the stringent starvation protein (SSP), we determined its N-terminal sequence as well as the sequence of two peptide fragments obtained by cyanogen bromide cleavage of the protein. We then chemically synthesized four sets of oligodeoxyribonucleotide mixtures that represented possible codon combinations for parts of these amino acid sequences. The synthetic oligonucleotides were labelled with ³²P at their 5-termini and used as hybridization probes to detect DNA fragments containing the complementary sequences. Genomic Southern hybridization of E. coli chromosomal DNA gave up to ten DNA fragments hybridizing with each probe but only a few hybridized with two or more of the probes. The latter fragments were coloned in pBR322. By determining partial base sequences with a rapid method and examining proteins encoded by the DNA fragments, we were able to show that we had isolated a clone containing the complete SSP structural gene.Abbreviations SSP stringent starvation protein - PTH phenylthiohydantoin     

The structure of nucleosome core particles as revealed by difference Raman spectroscopy.

Raman spectra have been observed of nucleosome core particles (I) prepared from chicken erythrocyte chromatin, its isolated 146 bp DNA (II), and its isolated histone octamer (H2A+H2B+H3+H4)2 (III). By examining the difference Raman spectra, (I)-(II), (I)-(III), and (I)-(II)-(III), several pieces of information have been obtained on the conformation of the DNA moiety, the conformation of the histone moiety, and the DNA-histone interaction in the nucleosome core particles. In the nucleosome core particles, about 15 bp (A.T rich) portions of the whole 146 bp DNA are considered to take an A-form conformation. These are considered to correspond to its bent portions which appear at intervals of 10 bp.     

Isolation of an actin polymerization stimulator from bovine thyroid plasma membranes

An actin polymerization stimulator was purified from bovine thyroid plasma membranes by DNase I affinity column chromatography. Although the molecular weight of the protein was about 42,000 (42K) by sodium dodecyl sulfate polyacrylamide gel electrophoresis, it did not comigrate with actin. In the presence of 30 mM KCl, the 42K protein facilitated formation of actin filaments when analyzed by a centrifugation method, accelerated the initial phase of actin polymerization as measured in an Ostwald viscometer and increased the length of filaments as shown by electron microscopy. The 42K protein also accelerated the initial phase of actin polymerization in the presence of 100 mM KCl and 2 mM MgCl₂ but did not affect the final viscosity. The effect of the 42K protein was diminished by 5 uM cytochalasin B or 1 uM cytochalasin D. This 42K protein may anchor actin filaments onto the thyroid plasma membrane.     

Raman diagnosis of nucleic acid structure: sugar-puckering and glycosidic conformation in the guanosine moiety.

Observations of Raman spectra of various nucleic acids indicate that the guanine ring breathing frequency is sensitive to the internal rotation angle around the glycosidic bond and to the conformation of the five-membered ring of the ribose residue that is directly connected with the guanine residue in question. It is found that 682 cm-1 for C2'-endo-anti, at 665 cm-1 for C3'-endo-anti, and at 625 cm-1 for C3'-endo-syn. A DNA octamer d(GpGpApApTpTpCpC) shows, in its aqueous solution, a broad Raman band at 680 cm-1 with a tail at 670 cm-1. This fact suggests that the guanosine residues in this oligomer take primarily C2'-endo-anti conformation but an appreciable amount of fluctuation of the ribose ring structure towards C3'-endo is involved.     

Inhibition of Thiamine Pyrophosphate Utilization by Thiamine or Its Monophosphate in Escherichia coli

The growth of a thiamine pyrophosphate auxotroph of Escherichi coli was inhibited by either thiamine or thiamine monophosphate, and the growth of a thiamine monophosphate auxotroph was inhibited by thiamine. The thiamine pyrophosphate-dependent oxidation of pyruvate was inhibited by thiamine with whole cells of the thiamine pyrophosphate auxotroph but not with cell extracts prepared from the same organism. In addition, the thiamine pyrophosphate uptake of the thiamine pyrophosphate auxotroph was inhibited by either thiamine or thiamine monophosphate. Although the thiamine pyrophosphate uptake of a revertant, selected for prototrophy from the thiamine monophosphate auxotroph, was inhibited by thiamine to an extent comparable to that observed with the thiamine monophosphate auxotroph, its growth was no longer inhibited by thiamine. A possible mechanism for the inhibition by thiamine and thiamine monophosphate in the utilization of thiamine pyrophosphate is discussed.