Thermostability, oligomerization and DNA-binding properties of the regulatory protein ArgR from the hyperthermophilic bacterium Thermotoga neapolitana

Abstract

The hexameric regulatory protein ArgR formed by arginine-mediated dimerization of identical trimers governs the expression of genes required for arginine metabolism and some other genes in mesophilic and moderately thermophilic bacteria. We have cloned the argR gene from two hyperthermophilic bacteria of the genus Thermotoga. The two-domain ArgR proteins encoded by T. neapolitana and T. maritima share a low degree of sequence similarity with other bacterial arginine repressors. The ArgR protein from T. neapolitana binds to an operator located just upstream of its coding sequence and, therefore, the argR gene may be autoregulated. The protein has extremely high intrinsic thermostability and tolerance to urea. Moreover, its binding to target DNA increases the melting temperature by approximately 15°C. The formation of oligomeric ArgR-DNA complexes is a function of protein concentration, with hexameric complexes being favoured at higher concentrations. In the presence of arginine the hyperthermophilic ArgR protein binds to its own operator, argRo, only by forming hexamer ArgR-DNA complexes, whereas both trimer-DNA and hexamer-DNA complexes are detected in the absence of arginine. However, the anity of T. neapolitana ArgR for DNA has been found to be higher for a mixture of trimers and non-bound hexamers than for argininebound hexamers. Our data indicate that genes for arginine biosynthesis are clustered in a putative operon, which could also be regulated by the ArgR protein, in the hyperthermophilic host.

Expression of STM4467 -Encoded Arginine Deiminase Controlled by the STM4463 Regulator Contributes to Salmonella enterica Serovar Typhimurium Virulence

“…This gene was formerly known as rosE, and the STM4463 protein was identified as a regulator that directly represses the expression of the std fimbrial operon (6). However, since homologs of STM4463 have been reported to regulate the expression of the ADI operon in other bacteria (12,33,34), we reasoned that the STM4463 protein might act as a regulator of Salmonella ADI expression. To examine STM4467 transcription, we constructed a strain that carried a transcriptional fusion of lacZ to the STM4467 gene.…”

Interaction between ArgR and AhrC Controls Regulation of Arginine Metabolism in Lactococcus lactis

“…Despite differences in the organization of genes involved in arginine metabolism, experimental evidence indicates that the mechanism of arginine-dependent regulation of these genes is highly conserved among a range of different organisms, including Gram-negative, Gram-positive and extremophilic bacteria (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Regulation is exerted by binding of single transcriptional regulators of the ArgR family to so-called ARG operator sites preceding the relevant target genes, generally leading to repression of arginine biosynthetic genes and activation of catabolic genes, in the presence of arginine.…”

Organization and Expression of a Thermus thermophilus Arginine Cluster: Presence of Unidentified Open Reading Frames and Absence of a Shine-Dalgarno Sequence

“…Nevertheless, regulation appears to be similar in most of these organisms: an ArgR repressor interacts with specific operator sequences (called Arg boxes) overlapping the promoter region (5,6,12,18,28). Homologous proteins were also reported to activate genes involved in arginine degradation in bacilli (19,20).…”