Purification and characterization of serine proteinase 2 from Bacillus intermedius 3-19.

A proteinase secreted in the late stationary phase was isolated from the culture fluid of Bacillus intermedius 3-19 by ion-exchange chromatography on CM-cellulose followed by FPLC on a Mono S column. The enzyme was completely inhibited by the serine proteinase inhibitors diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride. The maximum proteolytic activity against the synthetic chromogenic substrate Z-Ala-Ala-Leu-pNA was observed at pH 9.0. The molecular weight of the enzyme is 28 kD and its isoelectric point is 9.2. We have also determined pH- and thermostability and Km and kcat of this proteinase. The enzyme has been classified as a thiol-dependent serine proteinase. N-Terminal amino acid sequence (10 residues) and amino acid composition of the protein were also determined. By the mode of hydrolysis of peptide bonds in the oxidized B-chain of insulin, this enzyme is similar to the thiol-dependent serine proteinase 1 from B. intermedius 3-19 secreted during vegetative growth.

Isolation and characterization of glutamyl endopeptidase 2 from Bacillus intermedius 3-19.

The culture filtrate of Bacillus intermedius 3-19 was used for isolation by chromatography on CM-cellulose and Mono S columns of a proteinase that is secreted during the late stages of growth. The enzyme is irreversibly inhibited by the inhibitor of serine proteinases diisopropyl fluorophosphate, has two pH optima (7.2 and 9.5) for casein hydrolysis and one at pH 8.5 for Z-Glu-pNA hydrolysis. The molecular weight of the enzyme is 26.5 kD. The K(m) for Z-Glu-pNA hydrolysis is 0.5 mM. The temperature and pH dependences of the stability of the proteinase were studied. The enzyme was identified as glutamyl endopeptidase 2. The N-terminal sequence (10 residues) and amino acid composition of the enzyme were determined. The enzyme hydrolyzes Glu4-Gln5, Glu17-Asp18, and Cys11-Ser12 bonds in the oxidized A-chain of insulin and Glu13-Ala14, Glu21-Arg22, Cys7-Gly8, and Cys19-Gly20 bonds in the oxidized B-chain of insulin.

Study of the mechanism of action of p-chloromercuribenzoate on endonuclease from the bacterium Serratia marcescens.

The mechanism of action of p-chloromercuribenzoate (PCMB) on Serratia marcescens nuclease was investigated. The analysis showed that PCMB forms complexes with DNA. Binding of C7H5O2Hg+ to DNA changes the secondary structure of the DNA. These changes alter the enzymatic activity of S. marcescens nuclease, which was previously found to be sensitive to the secondary structure of the substrates. The nuclease activity was either suppressed or stimulated in the presence of PCMB depending on the C7H5O2Hg+ to nucleotide equivalent ratio. Binding of C7H5O2Hg+ to DNA did not form an abortive enzyme-substrate complex. Binding of Mg2+ to the C7H5O2Hg-DNA complex caused appropriate changes in secondary structure of the substrate. Since Mg2+ and C7H5O2Hg+, though differing in the type of metal cation, are similar in their mechanisms of influence on enzymatic activity of S. marcescens nuclease, the identity of other metal-containing effectors in their mechanism of action on Serratia marcescens nuclease is assumed.

Factors influencing the cellular location of proteolytic enzymes of Bacillus intermedius.

Thiol-dependent serine proteinase and glutamylendopeptidase of Bacillus intermedius 3-19 being prevailing enzymes in the total pool of extracellular proteinases (95%) of this microorganism in catalytic active form were detected on the membrane of the cells. Production of these enzymes was maximum on the medium containing inorganic phosphate and gelatin and decreased 2-4-fold on the medium with glucose and lactate. The level of the activity of extracellular enzymes correlated with that of corresponding membrane-bound proteins. The addition of CoCl2 (2 mM) into the medium caused essential increase in extracellular glutamylendopeptidase activity and promoted the release of membrane-bound enzyme into cultural fluid. Proteolytic activity was detected in cytoplasm also. Proteinases localized in cytoplasm were shown to differ in properties from those secreted.

Biosynthesis and localization of glutamylendopeptidase from Bacillus intermedius strain 3-19.

The biosynthesis of glutamylendopeptidase from Bacillus intermedius strain 3-19 and localization of the enzyme in the bacterial cells was studied. The synthesis of the enzyme was suppressed by easily metabolizable carbon sources. Inorganic phosphate and NH4+ ions stimulated the production of glutamylendopeptidase. Complicated organic substrates such as casein, gelatine, and haemoglobin did not affect the biosynthesis of the enzyme. The divalent metallic ions Ca2+, Mg2+, Co2+ increased the production of glutamylendopeptidase while Zn2+, Cu2+, and Fe2+ reduced the biosynthesis of proteinase. The rate of synthesis of the enzyme increased when the rate of the bacterial growth decreased. The maximum enzyme activity in the culture fluid was determined at the stationary phase of growth. In the cells glutamylendopeptidase was bound to the cytoplasmic membrane, and the maximal enzyme activity was detected in the stationary growth phase. The results facilitated the development of a medium which yielded the maximum glutamylendopeptidase production by B. intermedius strain 3-19.

Expression of the genes for guanyl-specific ribonucleases from Bacillus intermedius and Bacillus pumilus is regulated by the two component signal transduction system PhoP-PhoR in B. subtilis.

Promoters of the genes for guanyl-specific ribonucleases, secreted by B. intermedius (binase) and B. pumilus (Rnase Bp) in phosphate deficient conditions, contain regions similar to appropriate consensus sequences in promoters of the PHO regulated genes of B. subtilis. A number of genes expressed in response to phosphate starvation in B. subtilis are regulated by the two component signal transduction system PhoP-PhoR. Expression of recombinant genes for binase and RNase Bp in B. subtilis strains with mutations in the regulatory protein genes of the PHO regulon was studied. Their expression is strongly regulated by the regulatory proteins of the B. subtilis PHO regulon.

Isolation and properties of extracellular alkaline phosphatase from Bacillus intermedius.

Alkaline phosphatase (APase) was isolated from the culture liquid of the streptomycin-resistant strain of Bacillus intermedius S3-19 and purified as a homogeneous preparation by ion-exchange chromatography and FPLC. Electrophoresis and gel-filtration revealed that the active enzyme is a monomer with molecular weight of 46-47 kD. The enzyme possessed phosphomonoesterase and phosphodiesterase activities with maximal levels at pH 9.5 and 55 degreesC and was stable until 60 degreesC at pH 8.0-10.0. The isolated APase exhibits a broad specificity towards a wide variety of substrates. The effect of divalent metal ions and other reagents on its catalytic activities was studied. It was concluded that alkaline phosphatase of B. intermedius is similar to the secreted alkaline phosphatases from other Bacillus species in its physicochemical and catalytic properties.

Glutamyl endopeptidase of Bacillus intermedius strain 3-19. Purification, properties, and crystallization.

A homogeneous glutamyl endopeptidase splitting peptide bonds of glutamic and, rarely, of aspartic acid residues in peptides and proteins was isolated from Bacillus intermedius 3-19 culture filtrate using chromatography on CM-cellulose and Mono S. The enzyme molecular mass is 29 kD and the pI is 8.4. The proteinase is inhibited by DFP. The enzyme, like other glutamyl endopeptidases, reveals two pH optima (pH 7.5 and 9.0) for casein and one (pH 8.0) for Z-Glu-pNA hydrolysis. The K(m) for the hydrolysis of the latter substrate is 6 mM. The enzyme activity is optimal at 55 degrees C. The enzyme is stable in the pH range 6.5-11.0. Its N-terminal sequence shows 56% coinciding residues when compared with that of Bacillus licheniformis glutamyl endopeptidase. Crystal prisms or plates 0.25-0.3 x 0.15 x 0.07-0.1 mm have been grown using the vapor diffusion technique in a hanging drop followed by macroseeding. The crystals belong to the space group B2 with the following unit cell parameters: a = 69.59 A; b = 61.61 A; c = 56.11 A; gamma = 117.57 degrees. The X-ray data set to 1.7 A resolution has been collected on an automatic synchrotron (EMBL Hamburg Station).

Glutamyl endopeptidase of Bacillus intermedius, strain 3-19.

A homogeneous glutamyl endopeptidase splitting peptide bonds of glutamic, rarely of aspartic acid residues in peptides and proteins, was isolated from Bacillus intermedius 3-19 culture filtrate using chromatography on CM cellulose and Mono S. The enzyme molecular mass is equal to 29 kDa, pI 8.4. The protease is inhibited by diisopropylfluorophosphate. The enzyme, like other glutamyl endopeptidases, reveals two pH optima at pH 7.5 and 9.0 for casein and one at pH 8.0 for Z-Glu-pNA hydrolysis. A 6 mM K(m) is found for hydrolysis of the latter substrate. The enzyme activity optimum lies at 55 degrees C, and it is stable at pH 6.5-11.0. Its N-terminal sequence shows 56% coinciding residues when compared with that of Bacillus licheniformis glutamyl endopeptidase.

Enzymatic properties of thiol-dependent serine proteinase of Bacillus intermedius 3-19.

Effects of a thiol-dependent serine proteinase of Bacillus intermedius on peptide substrates and insulin B-chain were studied. The enzyme preferably splits peptide bonds formed by carboxyl groups of hydrophobic amino acids. Ca2+ increases the thermal stability of the proteinase significantly. The kinetic characteristics of hydrolysis of Z-Ala-Ala-Leu-pNA by this enzyme was determined as K(m) = 1.25 mM and kcat = 0.15 sec-1. The enzyme has high stability to DMFA and isopropanol, and is able to catalyze peptide bond synthesis.

[Actinomycin D influence on biosynthesis of extracellular ribonucleases by sporulating bacteria]. / Vliyanie aktinomitsina D na biosintez vnekletochnykh ribonukleaz sporoobrazuyushchikh bakteril

The influence of actinomycin D on the synthesis of extracellular ribonucleases by "Bacillus intermedius" (binase), B.pumilus (RNAse Bp) and B.amyloliquefaciens (barnase) was studied comparatively. When added during the active synthesis of the enzymes actinomycin D stimulated the biosynthesis of binase and RNAse Bp and had no influence on the barnase biosynthesis. The response of the bacillary RNAse biosynthesis to the added actinomycin D correlated with the differences in the nucleotide sequences of the genes encoding the enzymes. The Escherichia coli SURE recombinant strains carrying the plasmids with the genes of binase, RNAse Bp and barnase under different regulatory sequences, as well as the E.coli MC4100 recombinant strains carrying the plasmids with the beta-galactosidase gene under the promoters of the bacillary RNAse were isolated. However, the expression of the bacillary ribonuclease genes in the E.coli recombinant strains carrying the plasmids with the genes of the enzymes, as well as the expression of the beta-galactosidase gene from the promotors of the bacillary RNAses was not stimulated by actinomycin D irrespective of the dose and addition time.

Isoforms of Serratia marcescens nuclease. The role of Mg2+ in the hydrolysis mechanism.

Structural and functional differences between isoforms Sm1 and Sm2, a lack of influence of free Mg2+ on the isoform structures, formation of DNA-magnesium complex serving with great probability as a real substrate for the nuclease has been summarized on the basis of experimental data. Mg2+ forming a complex with phosphate groups of DNA are supposed to further increase the electrophilicity of the phosphorus atoms besides causing a conformational change of the substrate.

A novel Bacillus intermedius extracellular alkaline phosphatase: isolation, physico-chemical and catalytic characteristics.

A new alkaline phosphatase was obtained as homogeneous preparation from culture filtrate of the spore-forming Bacillus intermedius. B. intermedius phosphatase was shown to be monomer with molecular weight of 47 kDa. The enzyme possesses phosphomonoesterase and phosphodiesterase activities and exhibits a broad specificity towards a wide variety of substrates. The purified phosphatase had an optimum temperature of 50 degrees C, optimum pH of 9.5 and was stable until 60 degrees C at pH 8-10. The effect of divalent metal ions and thiol reagents on catalytic activity of the enzyme was studied.

Phosphate regulation of biosynthesis of extracellular RNases of endospore-forming bacteria.

The gene for the extracellular ribonuclease of B. pumilus KMM62 (RNase Bp) has been cloned and sequenced. The structural gene for this enzyme is similar to those of the extracellular ribonucleases of B. intermedius 7P (binase) and B. amyloliquefaciens H2 (barnase), as are the regulatory regions of binase and RNase Bp. The regulatory region of the barnase gene, however, is quite different from the other two. In the promoter of the genes for binase and RNase Bp, but not in that for barnase, is a region similar to the Pho box of E. coli. We have established that inorganic phosphate suppresses the synthesis of the binase and RNase Bp, but does not effect the synthesis of barnase.

Increase of specificity of RNase from Bacillus amyloliquefaciens (barnase) by substitution of Glu for Ser57 using site-directed mutagenesis.

Bacterial ribonucleases from Bacillus amyloliquefaciens and Bacillus intermedius show the specificity towards the nature of a nucleoside at the O3' end of the phosphodiester bond to be split in the preference order G > A >> U > C in the cleavage reactions of polynucleotides. It follows from the X-ray data that the substrate guanosine base is bound at the active site of these RNases in the same manner as for high-specificity guanylic RNases. We supposed that the difference in specificity for the two types of RNases is due to the additional hydrogen bond between the protein and a purine base in the case of bacterial guanyl-preferring RNases in contrast to the high-specificity guanylic RNases. To examine this hypothesis we prepared the Ser57 --> Glu mutant of B. amyloliquefaciens, in which this hydrogen bond is eliminated. Kinetic studies demonstrate that the specificity of this mutant towards guanylic substrates is 35-times greater than that of the wild-type RNases from B. amyloliquefaciens and close to that of RNases T1.

Comparative study of thermostability and structure of close homologues--barnase and binase.

Parameters of heat denaturation and intrinsic fluorescence of barnase and its close homologue, binase in the pH region 2-6 have been determined. The barnase heat denaturation (pH 2.8-5.5) proceeds according to the "all-or-none" principle. Barnase denaturation temperature is lower than that of binase and this difference increases from 2.5 degrees C at pH 5 to 7 degrees C at pH 3. Enthalpy values of barnase and binase denaturation coincide only at pH 4.5-5.5, but as far as pH decreases the barnase denaturation enthalpy decreases significantly and in this respect it differs from binase. The fluorescence and CD techniques do not reveal any distinctions in the local environment of aromatic residues in the two proteins, and the obtained difference in the parameters of intrinsic fluorescence is due to fluorescence quenching of the barnase Trp94 by the His 18 residue, absent in binase. Secondary structures of both native and denaturated proteins also do not differ. Some differences in the barnase and binase electrostatic characteristics, revealed in the character of the dipole moments distribution, have been found.