Abstract
Many bacterial species modify their DNA with the addition of sulfur to phosphate groups, a modification known as DNA phosphorothioation. DndA is known to act as a cysteine desulfurase, catalyzing a key biochemical step in phosphorothioation. However, bioinformatic analysis revealed that 19 out of the 31 known dnd gene clusters, contain only four genes (dndB-E), lacking a key cysteine desulfurase corresponding gene. There are multiple cysteine desulfurase genes in Escherichia coli, but which one of them participates into DNA phosphorothioation is unknown. Here, by employing heterologous expression of the Salmonella enterica dnd gene cluster named dptBCDE in three E. coli mutants, each of which lacked a different cysteine desulfurase gene, we show that IscS is the only cysteine desulfurase that collaborates with dptB-E, resulting in DNA phosphorothioation. Using a bacterial two-hybrid system, protein interactions between IscS and DptC, and IscS and DptE were identified. Our findings revealed IscS as a key participant in DNA phosphorothioation and lay the basis for in-depth analysis of the DNA phosphorothioation biochemical pathway.
Highlights
Sequence and stereo specific physiological DNA phosphorothioation occurs in many bacteria [1,2,3,4]
The dnd genes are usually located on genomic islands that were probably acquired by horizontal gene transfer [3]
The E.coli genome was searched for orthologs of a cysteine desulfurase gene
Summary
Sequence and stereo specific physiological DNA phosphorothioation occurs in many bacteria [1,2,3,4]. In Streptomyces lividans 1326, a five-gene cluster, dndA–E, determines the modification [1]. Orthologs of these genes were found in 30 bacterial species and one Archaea [2]. The dnd genes are usually located on genomic islands that were probably acquired by horizontal gene transfer [3]. Several of these gene clusters contain dndB-E homologues, but lack a dndA homologue [2,3]. In-frame deletion of dndA in S. lividans showed that the gene is essential for DNA phosphorothioation [1,4]. DndA was shown to be a cysteine desulfurase involved in the iron-sulfur cluster assembly for apo-Fe DndC [5]
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