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Biomedical subjects

S R Malkhos'ian

Publications and source records attributed to S R Malkhos'ian.

4 recordsLinked to original sources
PubMedDate not supplied

[Spontaneous synthesis of colicin].

We studied regularities of the spontaneous synthesis of colicin E1 and its regulatory role in the survival of each cell and the population. For the first time, colicin from spontaneously induced cells was isolated and characterized, and the kinetics of its synthesis determined in a separate cell. It was stated that the time of colicin accumulation in an induced cell and the half-time period of a similar cell exceeds the period of cell doubling by 1.5 and 2 times, respectively. Spontaneously synthesized colicin was shown not to differ from the colicin synthesized by using inductors of the SOS-system of cell reparation. A conception was formulated of a biological system containing both colicinogenic cells with plasmids with encoded proteins of colicin, immunity and lysis on them and competitive plasmid-free cells sensitive or resistant to colicin. Environment dependent colicin synthesis in the system shown is regarded as regulator functioning according to the feed-back principle.

Chromatography, Affinity↗
PubMedDate not supplied

[The effect of supercoiling of DNA from colicinogenic plasmids on the expression of col, imm and lys genes].

The expression of colicin genes is controlled by the SOS-system (Lex A repressor) and the adenylate-cyclase system (cAMP-CAP complex). The effect of plasmid DNA supercoiling on the expression of the operons of colicins E1, E2, and E3 has been studied by using E. coli minicells. It has been shown for the colicin E1 operon that it is the promoter that is influenced by supercoiling: an increase in negative supercoiling elevates the expression and, vice versa, DNA relaxation reduces the expression. The effect of supercoiling on gene activity of the colicin E1 immunity protein has not been observed, which may be due to the specific orientation of this gene. With the two other colicins supercoiling affects the expression of all genes which constitute the operon. The regulation of the colicin operon expression has been confirmed to occur at three levels: by the LexA protein, by the cAMP-CAP complex, and by the plasmid DNA supercoiling.

Bacterial Proteins↗