A maltose-regulated large genomic region is activated by the transcriptional regulator MalT in Actinoplanes sp. SE50/110

Julian Droste,Lena Schaffert,Martin Kulisch,Alfred Pühler,Susanne Schneiker-Bekel,Timo Wolf,Jörn Kalinowski

doi:10.1007/s00253-020-10923-2

Abstract

Actinoplanes sp. SE50/110 is the industrially relevant producer of acarbose, which is used in the treatment of diabetes mellitus. Recent studies elucidated the expression dynamics in Actinoplanes sp. SE50/110 during growth. From these data, we obtained a large genomic region (ACSP50_3900 to ACSP50_3950) containing 51 genes, of which 39 are transcribed in the same manner. These co-regulated genes were found to be stronger transcribed on maltose compared with glucose as a carbon source. The transcriptional regulator MalT was identified as an activator of this maltose-regulated large genomic region (MRLGR). Since most of the genes are poorly annotated, the function of this region is farther unclear. However, comprehensive BLAST analyses indicate similarities to enzymes involved in amino acid metabolism. We determined a conserved binding motif of MalT overlapping the -35 promoter region of 17 transcription start sites inside the MRLGR. The corresponding sequence motif 5′-TCATCC-5nt-GGATGA-3′ displays high similarities to reported MalT binding sites in Escherichia coli and Klebsiella pneumoniae, in which MalT is the activator of mal genes. A malT deletion and an overexpression mutant were constructed. Differential transcriptome analyses revealed an activating effect of MalT on 40 of the 51 genes. Surprisingly, no gene of the maltose metabolism is affected. In contrast to many other bacteria, MalT is not the activator of mal genes in Actinoplanes sp. SE50/110. Finally, the MRLGR was found partly in other closely related bacteria of the family Micromonosporaceae. Even the conserved MalT binding site was found upstream of several genes inside of the corresponding regions.Key points• MalT is the maltose-dependent activator of a large genomic region in ACSP50_WT.• The consensus binding motif is similar to MalT binding sites in other bacteria.• MalT is not the regulator of genes involved in maltose metabolism in ACSP50_WT.

Highlights

Forty-one genes of the maltose-regulated large genomic region are co-regulated in Actinoplanes sp
SE50/110 wild type strain grown on maltose compared with glucose minimal medium (Supplemental Fig. S1 and Supplemental Table S1)
By analyzing the top scorer of this experiment, it could be shown that the genes of the region ACSP50_3900 to ACSP50_3950 are among the genes with the highest M values

Summary

Introduction

SE50/110 is the natural producer of the pseudotetrasaccharide acarbose (acarviosyl-1,4-maltose), which functions as an α-glucosidase inhibitor and is used in the treatment of diabetes mellitus (Truscheit et al 1981). It is a Gram-positive, aerobic bacterium, which grows in branched hyphae and can form sporangia and motile spores (Vobis et al 2015). SE50/100 has a high G+C content of 71.32%, which was first sequenced by Schwientek et al (2012). A refined high-quality genome of Actinoplanes sp. SE50/110 is available (Wolf et al 2017b)

Methods

Results

Conclusion