Involvement of the Multidomain Regulatory Protein XynR in Positive Control of Xylanase Gene Expression in the Ruminal Anaerobe Prevotella bryantii B ₁ 4

Abstract

The xylanase gene cluster from the rumen anaerobe Prevotella bryantii B 1 4 was found to include a gene (xynR) that encodes a multidomain regulatory protein and is downstream from the xylanase and ␤-xylosidase genes xynA and xynB. Additional genes identified upstream of xynA and xynB include xynD, which encodes an integral membrane protein that has homology with Na:solute symporters; xynE, which is related to the genes encoding acylhydrolases and arylesterases; and xynF, which has homology with the genes encoding ␣-glucuronidases. XynR includes, in a single 833-amino-acid polypeptide, a putative input domain unrelated to other database sequences, a likely transmembrane domain, histidine kinase motifs, response regulator sequences, and a C-terminal AraC-type helix-turn-helix DNA binding domain. Two transcripts (3.7 and 5.8 kb) were detected with a xynA probe, and the start site of the 3.7-kb transcript encoding xynABD was mapped to a position upstream of xynD. The DNA binding domain of XynR was purified after amplification and overexpression in Escherichia coli and was found to bind to a 141-bp DNA fragment from the region immediately upstream of xynD. In vitro transcription assays demonstrated that XynR stimulates transcription of the 3.7-kb transcript. We concluded that XynR acts as a positive regulator that activates expression of xynABD in P. bryantii B 1 4. This is the first regulatory protein that demonstrates significant homology with the two-component regulatory protein superfamily and has been shown to be involved in the regulation of polysaccharidase gene expression.

Multiple Regulatory Mechanisms Control the Expression of the Geobacillus stearothermophilus Gene for Extracellular Xylanase

“…Other microorganisms have developed dedicated systems to sense the high molecular weight polysaccharides in the surrounding environments and to activate the corresponding genes. For example, in the rumen anaerobe Prevotella bryantii B14, the xylanase gene is up-regulated in response to xylan in the environment (23). This regulation is mediated by a multidomain protein, XynR, that contains a transmembrane domain, histidine kinase motif, response regulator sequence, and a DNA binding domain in its C terminus.…”

Biochemical Analysis of a β- d -Xylosidase and a Bifunctional Xylanase-Ferulic Acid Esterase from a Xylanolytic Gene Cluster in Prevotella ruminicola 23

“…Despite its documented importance in rumen physiology, relatively little is known about the cellular machinery that P. ruminicola 23 employs to harvest energy from hemicellulosic substrates. Several studies have explored the carbohydrate active enzymes from the related taxon Prevotella bryantii B 1 4 (previously classified as P. ruminicola B 1 4) (25,27,28,50,52,66,73); however, less is known about the xylanolytic system that P. ruminicola 23 elaborates. These two species share 88.9% nucleotide identity in their 16S rRNA genes (1,473 nucleotides aligned); however, there is evidence that these two species exhibit differences in their xylanolytic systems (2).…”

Identification and use of the putative Bacteroides ovatus xylanase promoter for the inducible production of recombinant human proteins

“…A possible ribosomebinding site (ATATAA) was located 12 bp upstream of the first ATG initiation codon of the operon (Fig. 2a), which was homologous to the first 5 bp of the putative consensus sequence of P. bryantii (Miyazaki et al, 2003). A similar AT-rich sequence was also observed 4-12 bp upstream of the start codon of all four xylan utilization genes (Fig.…”