In vitro maturation pathway of a glutamyl endopeptidase precursor from Bacillus licheniformis.

A gene encoding of glutamyl-specific endopeptidase precursor from Bacillus licheniformis has been cloned in Escherichia coli cells. The recombinant protein was expressed and accumulated as cytoplasmic insoluble inclusion bodies. Washed inclusion bodies were solubilized in 6 M guanidine-HCL in the presence of reducing agent. The following precursor renaturation was performed by fast frequent dilution method. The highest yield of the refolded protein was achieved at pH value of 8.5 and 4 degrees C. The renaturation process was accompanied by a gradual splitting of Glu(-48)/Thr(-47) and Glu(-13)/Lys(-12) peptide bonds. A 26-kDa protein proved to be an end product of in vitro renaturation. The mature glutamyl endopeptidase with a molecular mass of 25 kDa was obtained after a limited proteolysis of the 26-kDa protein was performed by subtilisin or trypsin. The 26-kDa protein was purified by gel filtration on a Superdex 75 column. Comparative characteristics of the thermal stability and catalytic properties of the 26-kDa and 25-kDa proteins showed that complete cleavage of the N-terminal pro-peptide by exogenous proteinase is necessary for a final packing and activation of the B. licheniformis glutamyl endopeptidase.

[Characterization of S1' subsite specificity of Thermoactinomyces vulgaris carboxypeptidase T by site-directed mutagenesis]. / Izuchenie S1'-karmana pervichnoi spetsifichnosti karboksipeptidazy T Thermoactinomyces vulgaris metodom napravlennogo mutageneza.

The site-directed mutagenesis in the S1'-pocket of Thermoactinomyces vulgaris carboxypeptidase T was performed and two variants containing double D253S, T255D and single T255D mutations were obtained. Precursors of the wild-type carboxypeptidase T and its mutant derivatives were expressed in Escherichia coli as inclusion bodies, refolded, activated by subtilisin, purified by gel efiltration on Superdex G-75. The catalytic activity with tripeptide substrates DNPAAR and ZAAL was analysed. The introduction of the aspartic residue in 255 position (like to mammalian carboxypeptidase B), insigniticantly enzymatic activity of the double mutant towards both substrates, as measured by Km and Kcat. An addition of the aspartic residue into S1'-binding pocket did not affect single mutant binding with the basic substrate while the Km value for the hydrophobic substrate increased approximately 40 times as compared with wild-type carboxypeptidase T and attained a level comparable with carboxypeptidase B.

Expression of bacillar glutamyl endopeptidase genes in Bacillus subtilis by a new mobilizable single-replicon vector pLF.

The pLF1311 natural plasmid from Lactobacillus fermentum 1311 was used to construct a single-replicon vector suitable for rapid cloning in a wide range of gram-positive hosts and Escherichia coli. The new vector is capable of conjugative mobilization from E. coli to various hosts by conjugal transfer. The final vector (3.4 kb) showed a high segregational and structural stability and a high copy number. Glutamyl endopeptidase genes from Bacillus licheniformis (gseBL) and B. intermedius (gseBI) were cloned in both pLF9 and pLF14 vectors and introduced to B. subtilis. The yield of enzymes in the pLF-derived producers was 6- to 30-fold more than in the natural producers and reached 100-150 mg/L of mature protease.

Introduction of a mini-gene encoding a five-amino acid peptide confers erythromycin resistance on Bacillus subtilis and provides temporary erythromycin protection in Proteus mirabilis.

A 15-bp mini-gene was introduced into Bacillus subtilis and into stable protoplast-like L-forms of Proteus mirabilis. This mini-gene encoded the peptide MVLFV and modeled a fragment of Escherichia coli 23S rRNA responsible for E. coli erythromycin (Ery) resistance. Expression of the introduced mini-gene conferred permanent Ery resistance on B. subtilis. In L-forms of P. mirabilis, the Ery-protective effect was maintained in the course of several generations. Herewith, the mechanism of Ery resistance mediated by expression of specific short peptides was shown to exist in evolutionary distant bacteria. Three new plasmids were constructed containing the gene under study transcriptionally fused with the genes encoding glutamylendopeptidase of Bacillus licheniformis or delta-endotoxin of Bacillus thuringiensis. The Ery resistance pentapeptide (E-peptide) mini-gene served as an efficient direct transcriptional reporter and allowed to select bacillar glutamylendopeptidase with improved productivity. The mini-genes encoding E-peptides may be applied as selective markers to transform both Gram-positive and Gram-negative bacteria. The small size of the E-peptide mini-genes makes them attractive selective markers for vector construction.

[Bacillus cereus chitinases: isolation and characteristics]. / Khitinazy Bacillus cereus: vydelenie i kharakteristika.

Three chitinases (M(r) = 68, 52 and 38 kDa) have been isolated from the cultural filtrate of Bacillus cereus strain VKPM B-6838 by stepwise hydrophobic chromatography on butyl-Toyopearl and gel filtration on Superdex 75 (FPLC). The chitinases are stable in the pH range 4-10 and have the same pH optimum of activity. The 68 and 38 kDa enzymes display the highest activity at 60 degrees C. while the 52 kDa chitinase-at 50 degrees C. In contrast with the 68- and 52 kDa enzymes, the 38 kDa chitinase hydrolyzes not only colloidal but also "crystalline" chitin and chitosan. None of the chitinases hydrolyzes chitobiose. The N-terminal sequences (10 amino acids) of the 52 and 38 kDa chitinases do not reveal structural similarity between themselves or to other known bacterial chitinases. The 68 kDa chitinase is not immunologically related to the 52 and 38 kDa enzymes. The results obtained suggest that the 68, 52 and 38 kDa chitinase are the unique proteins.