Abstract
In Archaea and Bacteria, gene expression is tightly regulated in response to environmental stimuli. In the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius nutrient limitation induces expression of the archaellum, the archaeal motility structure. This expression is orchestrated by a complex hierarchical network of positive and negative regulators—the archaellum regulatory network (arn). The membrane-bound one-component system ArnR and its paralog ArnR1 were recently described as main activators of archaellum expression in S. acidocaldarius. They regulate gene expression of the archaellum operon by targeting the promoter of flaB, encoding the archaellum filament protein. Here we describe a strategy for the isolation and biochemical characterization of these two archaellum regulators. Both regulators are capable of forming oligomers and are phosphorylated by the Ser/Thr kinase ArnC. Apart from binding to pflaB, ArnR but not ArnR1 bound to promoter sequences of aapF and upsX, which encode components of the archaeal adhesive pilus and UV-inducible pili system, demonstrating a regulatory connection between different surface appendages of S. acidocaldarius.
Highlights
Stress response that yields adaptation to changing environmental conditions is one of the most important prerequisites to ensure survival in prokaryotes
ArnR and ArnR1 were solely detected in the E. coli membrane fraction (Fig. 2A), which was used further for protein purification via Nickel-affinity chromatography coupled to desalting of eluted protein samples (Fig. 2A, middle)
Neither ArnR nor ArnR1 showed binding to pSaci_2122, supporting the idea that ArnR and ArnR1 exclusively regulate T4P related promoters. Taken together these results suggest that ArnR is involved in regulation of the archaellum, the archaeal adhesive pilus (Aap)- and UV-inducible pili system (Ups)-pilus of S. acidocaldarius while ArnR1 exclusively exerts its function in the archaellum
Summary
Stress response that yields adaptation to changing environmental conditions is one of the most important prerequisites to ensure survival in prokaryotes. Various signal transduction modules have evolved to receive, transfer and process extracellular signals in the cell (Esser et al, 2016; Koretke et al, 2000; Ulrich, Koonin & Zhulin, 2005) In response to these signals, transcription factors regulate and adjust gene expression to ensure cellular survival. Conditions under which expression of arnR1 is induced are unknown, whereas transcription of arnR increases upon nutrient limitation Both proteins presumably target the flaB promoter, which harbors two conserved cis-regulatory elements called ArnR
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