The crystal structure of metallocarboxypeptidase T (CPT) from Thermoactinomyces vulgaris in complex with L-phenyl lactate was determined at 1.73 Å resolution. As opposed to pancreatic carboxypeptidase A, which binds one L-phenyl lactate molecule, the ligand in the complex with CPT occupies simultaneously the S1 and S' subsites of the active site. This leads to conformational changes, which differ from those caused by the alternating occupation of the S1 and S1' subsites by tert-butyloxycarbonyl-L-leucine (BOC-leucine) and benzylsuccinic acid. These changes concern the residues E277, E59, L254, G192, S127, and Y218 and are up to 0.77 Å. A conclusion was drawn about the possible role of the residue E59 in the substrate recognition and catalysis by carboxypeptidase Т.

Crystals of mutant carboxypeptidase T from Thermoactinomyces vulgaris (CPT11QG) with amino-acid substitutions G215S, Q249G, A251G, T257A, D260G, T262D, and L254I and with the insertion ins253T were grown in microgravity by the capillary counter-diffusion method. The crystals belong to sp. gr. P31, which differs from the space group of the wild-type enzyme (P6322). The X-ray diffraction data set was collected from the crystals at the SPring-8 synchrotron facility (Japan) and is suitable for crystal structure determination at 2.45 Å resolution.

It is generally accepted that the primary specificity of metallocarboxypeptidases is mainly determined by the structure of the so–called primary specificity pocket. However, the G215S/A251G/T257A/D260G/T262D mutant of carboxypeptidase T from Thermoactinomyces vulgaris (CPT) with the primary specificity pocket fully reproducing the one in pancreatic carboxypeptidase B (CPB) retained the broad, mainly hydrophobic substrate specificity of the wild–type enzyme. In order to elucidate factors affecting substrate specificity of metallocarboxypeptidases and the reasons for the discrepancy with the established views, we have solved the structure of the complex of the CPT G215S/A251G/T257A/D260G/T262D mutant with the transition state analogue N–sulfamoyl–L–phenylalanine at a resolution of 1.35 Å and compared it with the structure of similar complex formed by CPB. The comparative study revealed a previously underestimated structural determinant of the substrate specificity of metallocarboxypeptidases and showed that even if substitution of five amino acid residues in the primary specificity pocket results in its almost complete structural correspondence to the analogous pocket in CPB, this does not lead to fundamental changes in the substrate specificity of the mutant enzyme due to the differences in the structure of the mobile loop located at the active site entrance that affects the substrate–induced conformational rearrangements of the active site.

The modified asparaginase Was79 was derived from the recombinant wild-type l-asparaginase of Wolinella succinogenes. The Was79 contains the amino acid substitutions V23Q and K24T responsible for the resistance to trypsinolysis and the N-terminal heparin-binding peptide KRKKKGKGLGKKR responsible for the binding to heparin and tumor K562 cells in vitro. When tested on a mouse model of Fischer lymphadenosis L5178Y, therapeutic efficacy of Was79 was significantly higher than that of reference enzymes at all single therapeutic doses used (125–8000 IU/kg). At Was79 single doses of 500–8000 IU/kg, the complete remission rate of 100 % was observed. The Was79 variant can be expressed intracellularly in E. coli as a less immunogenic formyl-methionine-free form at high per cell production levels.

A metallocarboxypeptidase produced by Streptomyces bikiniensis 27 strain (VKPM Ac-1783) (CPSb) was purified and characterized. The enzyme cleaves both basic and hydrophobic C-terminal amino acid residues from synthetic peptides, that is, it possesses specificity of mammalian carboxypeptidases A and B. The enzyme also hydrolyzes peptides bearing glutamic acid at the C-end. CPSb exhibits its maximal activity at pH 7.0–7.6 and 55°C. The nucleotide sequence encoding the mature CPSb in S. bikiniensis 27 (VKPM Ac-1783) genome (Accession No. GU362077) was determined. It is shown that the primary structure of the mature enzyme has a moderate degree of identity with orthologs from Streptomyces griseus (79% identity) and Streptomyces avermitilis (85% identity).

Выделена и охарактеризована металлокарбоксипептидаза, продуцируемая штаммом Streptomyces bikiniensis 27 (ВКПМ Ас-1783) (КПSb). Фермент способен c равной эффективностью отщеплять от синтетических пептидов как основные, так и гидрофобные С-концевые остатки, т.е. обладает специфичностью карбоксипептидаз А и В млекопитающих. Фермент также гидролизует пептиды, имеющие на С-конце глутаминовую кислоту. КПSb имеет максимальную активность при рН 7,0-7,6 и 55°. Установлена последовательность участка ДНК, соответствующего зрелому ферменту КПSb в геноме S. bikiniensis 27 (ВКПМ Ас-1783) (Accession No GU362077). Показано, что первичная структура зрелого фермента имеет умеренную степень идентичности с ортологами из Streptomyces griseus (79% идентичности) и Streptomyces avermitilis (85% идентичности).

The gene of microbial lysozyme (lyz) of S. aureus 118 and the gene of lysostaphin (lzf) of S. aureus RN 3239 were cloned and their expression in B. subtilis cells was shown. Lysozyme production in B. subtilis recombinant clone pLF14-Lyz, obtained as the result of cloning, was 2.5-fold greater than lysozyme production in S. aureus wild strain 118. Lysostaphin production in B. subtilis recombinant strain pLF14-Lzf which had inherited the cloned genes was approximately equal to lysostaphin production observed in S. aureus initial strain RN 3239. The production of lysozyme and lysostaphin in the cells of B. subtilis recombinant strains was observed at 30 degrees C and pH 5.5, while in S. aureus initial strains 118 and RN 3239 bacteria produced lysozyme and lysostaphin at 37 degrees C and pH 7.5 respectively.

Functional destination of propeptides and precursors in bacillar secretory proteases remains uncertain. Formerly deletion assay demonstrated folding and secretion of subtilisin E, chymotrypsin-like protease SGPB from S. griseus and B. cereus metalloprotease to depend on full-length propeptide in the precursors. Actually an artificial B. amyloliquefaciens metalloprotease gene with deletion of 51 amino acid residues from N-terminus was constructed with regard to carry out functional mapping of secretory metalloprotease propeptides. B. subtilis wprA gene 5'-terminal region spanning promoter and secretory leader was coupled to provide transcription to the truncated gene and secretion to its product. B. subtilis clones bearing a plasmid with the modified gene synthesised an active mature metalloprotease.

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 δ-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.