1022-7954/01/3710- $25.00 © 2001
Russian Journal of Genetics, Vol. 37, No. 10, 2001, pp. 1123–1129. Translated from Genetika, Vol. 37, No. 10, 2001, pp. 1340–1347.
Original Russian Text Copyright © 2001 by Luzhetskii, Ostash, Fedorenko.
Actinomycetes produce a broad spectrum of biolog-
ically active substances, in particular, many known
antibiotics [1, 2]. Researches has been permanently
searching for producers of new antibiotics among these
bacteria. This is related to the increasingly frequent
appearance of clinical strains of microorganisms that
are causative agents of contagious diseases resistant to
widely used antibiotics and of tumor cells with the mul-
tiple drug-resistance phenotype .
1912 strain of actino-
mycetes is a producer of the antitumor antibiotic lando-
mycin E (LE; Fig. 1) that belongs to a group of angucy-
clines. These antibiotics, together with antracyclines,
are the largest group of compounds in the class of aro-
matic polyketide antibiotics. All representatives of this
group express antitumor activity to some extent .
Landomycins are characterized by an unusual spectrum
of antitumor properties (in particular, they act against
antracycline-resistant tumor cells and prostatic gland
adenoma). Genetic and biochemical control of the bio-
synthesis of angucyclines is little studied, especially at
the modiﬁcation stage of the primary polyketide chain.
However, it is known that these reactions determine the
nature of biological action of polyketide antibiotics [1, 3].
To date, the LE biosynthetic gene cluster (
ter; Fig. 2) has been cloned and partially sequenced .
Further analysis of the genetic control of LE synthesis
will provide insights into its mechanism. The construc-
tion of recombinant strains carrying antibiotic biosyn-
thetic genes cloned from various actinomycetes (com-
binatory biosynthesis) is promising for obtaining new
drugs . The success of this approach will depend on
the available “arsenal” of cloned genes, a combination
of which can lead to the production of “hybrid” antibi-
Using Integrative Plasmid pSET152 and Its Derivatives
A. N. Luzhetskii, B. E. Ostash, and V. A. Fedorenko
Ivan Franko National University of Lviv, 79005 Ukraine; e-mail: email@example.com
Received March 21, 2001
1912 produces a novel angucycline antitumor antibiotic landomycin E
(LE). To study the LE biosynthetic gene cluster in detail, a system for the conjugal transfer of the integrative
plasmid pSET152 from
1912 has been developed. It was shown that this
plasmid integrates into two sites of the
chromosome and is stably inherited under nonselective
exconjugants of the strain 1912 are characterized by a signiﬁcant decrease in LE synthe-
sis (by 50–90%). A negative effect of pSET152 integration on antibiotic production was observed even upon
the use of the recipient strain with increased LE synthesis, although in this case, the level of LE production in
exconjugants was 120–150% of that in the original strain 1912. Based on pSET152, a vector system for gene
was developed. The effectivity of this system was shown in the example of disrup-
tion of the
gene encoding the key enzyme of LE synthesis (
-ketoacylsynthase). Inactivation of this gene
was shown to lead to the cessation of LE biosynthesis.
Structural formula of landomycin E .