Abstract
BackgroundAcarbose is used in the treatment of diabetes mellitus type II and is produced by Actinoplanes sp. SE50/110. Although the biosynthesis of acarbose has been intensively studied, profound knowledge about transcription factors involved in acarbose biosynthesis and their binding sites has been missing until now. In contrast to acarbose biosynthetic gene clusters in Streptomyces spp., the corresponding gene cluster of Actinoplanes sp. SE50/110 lacks genes for transcriptional regulators.ResultsThe acarbose regulator C (AcrC) was identified through an in silico approach by aligning the LacI family regulators of acarbose biosynthetic gene clusters in Streptomyces spp. with the Actinoplanes sp. SE50/110 genome. The gene for acrC, located in a head-to-head arrangement with the maltose/maltodextrin ABC transporter malEFG operon, was deleted by introducing PCR targeting for Actinoplanes sp. SE50/110. Characterization was carried out through cultivation experiments, genome-wide microarray hybridizations, and RT-qPCR as well as electrophoretic mobility shift assays for the elucidation of binding motifs. The results show that AcrC binds to the intergenic region between acbE and acbD in Actinoplanes sp. SE50/110 and acts as a transcriptional repressor on these genes. The transcriptomic profile of the wild type was reconstituted through a complementation of the deleted acrC gene. Additionally, regulatory sequence motifs for the binding of AcrC were identified in the intergenic region of acbE and acbD. It was shown that AcrC expression influences acarbose formation in the early growth phase. Interestingly, AcrC does not regulate the malEFG operon.ConclusionsThis study characterizes the first known transcription factor of the acarbose biosynthetic gene cluster in Actinoplanes sp. SE50/110. It therefore represents an important step for understanding the regulatory network of this organism. Based on this work, rational strain design for improving the biotechnological production of acarbose can now be implemented.
Highlights
Acarbose is used in the treatment of diabetes mellitus type II and is produced by Actinoplanes sp
Profound knowledge about transcription factors involved in acarbose biosynthesis and their binding sites is missing until now
Profound knowledge about transcription factors involved in acarbose biosynthesis and their binding sites was missing until now
Summary
Acarbose is used in the treatment of diabetes mellitus type II and is produced by Actinoplanes sp. In contrast to acarbose biosynthetic gene clusters in Streptomyces spp., the corresponding gene cluster of Actinoplanes sp. Acarbose (acarviosyl-1,4-maltose) is used for the treatment of diabetes mellitus type II, as it supports the reduction of blood sugar levels, due to its inhibitory effect on alphaglucosidases in the human intestine [1,2,3]. SE50/110 is a natural producer of the pseudotetrasaccharide acarbose and the genome includes the acarbose biosynthetic (acb) gene cluster [4, 5]. Actinoplanes species are characterized by genomes with high G + C contents of 69–73%, can produce motile spores and typically grow in branched hyphae [7, 8]
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