Involvement of the multidomain regulatory protein XynR in positive control of xylanase gene expression in the ruminal anaerobe Prevotella bryantii B14
Involvement of the multidomain regulatory protein XynR in positive control of xylanase gene expression in the ruminal anaerobe Prevotella bryantii B14
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DOI：
10.1128/jb.185.7.2219-2226.2003
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发表时间：
2003-04-01
影响因子：
3.2
通讯作者：
Flint, HJ
中科院分区：
文献类型：
--
作者：
Miyazaki, K;Miyamoto, H;Flint, HJ
发现来自瘤胃厌氧菌布氏普雷沃氏菌（Prevotella bryantii）B（I）4的木聚糖酶基因簇包括编码多结构域调节蛋白的基因（xynR），该基因位于木聚糖酶和β-木糖苷酶基因xynA和xynB的下游。在xynA和xynB上游鉴定的其他基因包括xynD，其编码与Na：溶质同向转运体具有同源性的整合膜蛋白; xynE，其与编码酰基水解酶和芳基酯酶的基因相关;和xynF，其与编码α-葡萄糖醛酸苷酶的基因具有同源性。XynR在单个833个氨基酸的多肽中包括与其他数据库序列无关的推定输入结构域、可能的跨膜结构域、组氨酸激酶基序、反应调节序列和C末端AraC型螺旋-转角-螺旋DNA结合结构域。用xynA探针检测两个转录物（3.7和5.8kb），并且将编码xynABD的3.7-kb转录物的起始位点映射到xynD的上游位置。在大肠杆菌中扩增和过表达后纯化XynR的DNA结合结构域，并发现其与紧邻xynD上游区域的141-bp DNA片段结合。体外转录试验表明，XynR刺激3.7 kb的转录本的转录。我们得出结论，XynR作为激活布氏肺孢子虫B（I）4中xynABD表达的正调节因子。这是第一个与双组分调节蛋白超家族具有显著同源性的调节蛋白，并已被证明参与多糖酶基因表达的调节。
The xylanase gene cluster from the rumen anaerobe Prevotella bryantii B(I)4 was found to include a gene (xynR) that encodes a multidomain regulatory protein and is downstream from the xylanase and P-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 alpha-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(I)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.