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Genetic interrelations in the actinomycin biosynthetic gene clusters of Streptomyces antibioticus IMRU 3720 and Streptomyces chrysomallus ATCC11523, producers of actinomycin X and actinomycin C

Authors Crnovčić I, Rückert C, Semsary S, Lang M, Kalinowski J, Keller U

Received 20 July 2016

Accepted for publication 9 February 2017

Published 7 April 2017 Volume 2017:10 Pages 29—46


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 3

Editor who approved publication: Dr Juan Fernandez-Recio

Ivana Crnovčić,1 Christian Rückert,2 Siamak Semsary,1 Manuel Lang,1 Jörn Kalinowski,2 Ullrich Keller1

1Institut für Chemie, Technische Universität Berlin, Berlin-Charlottenburg, 2Technology Platform Genomics, Center for Biotechnology, Bielefeld University, Bielefeld, Germany

Abstract: Sequencing the actinomycin (acm) biosynthetic gene cluster of Streptomyces antibioticus IMRU 3720, which produces actinomycin X (Acm X), revealed 20 genes organized into a highly similar framework as in the bi-armed acm C biosynthetic gene cluster of Streptomyces chrysomallus but without an attached additional extra arm of orthologues as in the latter. Curiously, the extra arm of the S. chrysomallus gene cluster turned out to perfectly match the single arm of the S. antibioticus gene cluster in the same order of orthologues including the the presence of two pseudogenes, scacmM and scacmN, encoding a cytochrome P450 and its ferredoxin, respectively. Orthologues of the latter genes were both missing in the principal arm of the S. chrysomallus acm C gene cluster. All orthologues of the extra arm showed a G +C-contents different from that of their counterparts in the principal arm. Moreover, the similarities of translation products from the extra arm were all higher to the corresponding translation products of orthologue genes from the S. antibioticus acm X gene cluster than to those encoded by the principal arm of their own gene cluster. This suggests that the duplicated structure of the S. chrysomallus acm C biosynthetic gene cluster evolved from previous fusion between two one-armed acm gene clusters each from a different genetic background. However, while scacmM and scacmN in the extra arm of the S. chrysomallus acm C gene cluster are mutated and therefore are non-functional, their orthologues saacmM and saacmN in the S. antibioticus acm C gene cluster show no defects seemingly encoding active enzymes with functions specific for Acm X biosynthesis. Both acm biosynthetic gene clusters lack a kynurenine-3-monooxygenase gene necessary for biosynthesis of 3-hydroxy-4-methylanthranilic acid, the building block of the Acm chromophore, which suggests participation of a genome-encoded relevant monooxygenase during Acm biosynthesis in both S. chrysomallus and S. antibioticus.

Keywords: actinomycin, actinomycin halves, biosynthesis, Streptomyces chrysomallus, ­Streptomyces anulatus Streptomyces antibioticus, genomes, 3-hydroxy-4-methylanthranilic acid (4-MHA), evolution of biosynthetic gene cluster, genetic transmission of biosynthetic gene cluster, actinomycin C, actinomycin X

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