Characterization of the Streptococcus gordonii chromosomal region immediately downstream of the glucosyltransferase gene.
Characterization of the Streptococcus gordonii chromosomal region immediately downstream of the glucosyltransferase gene.
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DOI：
10.1099/00221287-147-11-3061
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发表时间：
2001-11
期刊：
影响因子：
1.5
通讯作者：
M. Vickerman;P. Minick;N. Mather
中科院分区：
文献类型：
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作者：
M. Vickerman;P. Minick;N. Mather
戈登链球菌葡萄糖基转移酶基因gtfG受上游决定子rgg的正调控。在本研究中，两个ORF，转录的相对的DNA链，被确定为直接下游的gtfG。第一个，指定dsg，与gtfG共享一个会聚的推定转录终止子，并编码一个预测的46 kDa的跨膜蛋白，类似于参与多糖生物合成的小肠结肠炎耶尔森氏菌TrsA。dsg的插入失活导致葡糖基转移酶活性只有亲本水平的大约60%。dsg 5'端的870 bp基因与gtfG调控决定簇相似。指定rggD，这rgg样决定簇下游的gtfG编码一个推定的33.6 kDa的胞质蛋白。尽管它们的序列相似，但rgg和rggD的功能似乎是特异的。其中rggD被插入失活的菌株和含有质粒携带的rggD的菌株具有亲本水平的葡糖基转移酶活性。北方印迹杂交分析表明，约1.3 kb的dsg特异性和约1.0 kb的rggD特异性mRNA转录本与该区域相关，没有观察到多顺反子转录本。虽然rgg样基因产物已被证明在几种链球菌中作为邻近基因的正转录调节因子，但北方印迹分析表明，在本研究的条件下，rggD不影响dsg或下游趋异的ylbN样决定簇的转录。与此相比，S。gordonii染色体区域与其他链球菌基因组的同源性，这些链球菌基因组不包含参与葡聚糖合成的rgg/rggD侧翼区域，这提出了关于该染色体区域起源的有趣的可能性，并且还表明rggD可能调节远端定位的基因。
The Streptococcus gordonii glucosyltransferase gene, gtfG, is positively regulated by the upstream determinant rgg. In the present study, two ORFs, transcribed on the opposite DNA strand, were identified immediately downstream of gtfG. The first, designated dsg, shares a convergent putative transcriptional terminator with gtfG, and encodes a predicted 46 kDa transmembrane protein similar to the Yersinia enterocolitica TrsA involved in polysaccharide biosynthesis. Insertional inactivation of dsg resulted in only approximately approximately 60% of the parental level of glucosyltransferase activity. The 870 bp gene 5' to dsg is similar to the gtfG regulatory determinant. Designated rggD, this rgg-like determinant downstream of gtfG encodes a putative 33.6 kDa cytoplasmic protein. Despite their sequence similarity, the functions of rgg and rggD appear specific. Strains in which rggD was insertionally inactivated and strains containing plasmid-borne rggD had parental levels of glucosyltransferase activity. Northern blot hybridization analyses showed approximately 1.3 kb dsg-specific and approximately 1.0 kb rggD-specific mRNA transcripts associated with this region; no polycistronic transcript was observed. Although rgg-like gene products have been demonstrated to function as positive transcriptional regulators of adjacent genes in several streptococcal species, Northern blot analysis suggested that rggD did not influence the transcription of dsg or the divergent downstream ylbN-like determinant under the conditions in the present study. Comparison of this S. gordonii chromosome region to other streptococcal genomes, which do not contain the rgg/rggD-flanked region involved in glucan synthesis, raised intriguing possibilities about the origins of this chromosomal region, and also suggested that rggD might regulate a distally located gene.