[The role of genes of the system of mismatched base correction in genetic recombination of Escherichia coli]. / Ob uchastii genov sistemy korrektsii nesparennykh osnovanii v geneticheskoi rekombinantsii E. coli.

A genetic system was elaborated to study intramolecular recombination of bacteriophages lambda and phi 80. Practically, the ideal complementation of nucleotide sequences in recombining DNA molecules is required to obtain recombinants resulting from RecA-dependent recombination in Escherichia coli cells. a hypothesis is proposed to which the correction of mismatched bases hinders recombinant formation during recombination of fully homologous DNAs. The increased yields of hybrid molecules during interaction of the same DNA in the cells with deficient genes for correction support the hypothesis as well as independent demonstration of mutation in a gene for correction according to the effect of the increased yield of recombinants. A series of Escherichia coli cells mutants with increased formation of recombinant clones has been obtained.

[Cloning and detailed mapping of the fra-ymt region of the Yersinia pestis pFra plasmid]. / Klonirovanie i detal'noe kartirovanie fra-ymt-oblasti plazmidy pFra Yersinia pestis.

The genetical libraries of the pFra plasmid of Yersinia pestis genes were obtained by insertion into the PstI, SalGI, EcoRI, XhoI restriction sites of the cosmid vector pHC79. The immunochemical analysis of the recombinant clones has revealed the clones synthesizing the antigen Fl (fraction I) and mouse toxin (Ymt--Yersinia pestis murine toxin). The restriction analysis of the plasmids from antigen synthesizing clones has permitted to construct the detailed physical map of the fra-ymt region of the pFra plasmid the size of 22 kb. The recombinant F1 positive clones of Escherichia coli are able to form at 37 degrees C the capsule-like structure peculiar for Yersinia pestis. The antigen F1 and the mouse toxin were isolated, purified and characterized. The antigen F1 is an 1-2 Md polymer containing a 16 kDa protein subunit. The mouse toxin a 240 kDa protein consisting of 61 kDa subunits. The nucleotide sequence of ymt gene has been defined.

[Specific proteolysis by fibrinolysin-coagulase from Yersinia pestis of Yersinia pseudotuberculosis outer membrane proteins coded by the Ca(2+)-dependence plasmid]. / Spetsificheskii proteoliz fibrinolizinokoagulazoi Yersinia pestis belkov vneshnei membrany, kodiruemykh plazmidoi Ca(2+)-zavisimosti v Yersinia pseudotuberculosis.

The pesticinogenicity 9.5 kb plasmid from Yersinia pestis strain EV76 has been marked by the kanamycin phosphotransferase gene inserted into PstI site and designated pP3. The obtained plasmid pP3 determines the synthesis of 45 kd pesticin, alpha and beta-forms of fibrinolysin coagulase (37 and 35 kd) and the 29, 19 and 13 kd proteins in Escherichia coli mini cells. When transferred into Yersinia pseudotuberculosis strain 6933 the plasmid causes the proteolysis of outer membrane proteins. The 150 kd protein is reduced to 138 kd, the 48.5 kd protein is reduced to 45 kd. The proteins secreted into the cultural medium (51 and 38 kd) are also cleaved. The proteolysis of the 150 kd protein was found to occur at the stage of secretion via the inner membrane. The purified fibrinolysin coagulase from Escherichia coli strain JM83 harbouring the plasmid pP3 induces the proteolysis in vitro of the isolated membrane proteins from Yersinia pseudotuberculosis strain 6953 similar to the proteolysis registered in vivo.