A sigmaB-like factor responsible for carotenoid biosynthesis in Streptomyces griseus.
A sigmaB-like factor responsible for carotenoid biosynthesis in Streptomyces griseus.
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一种负责灰色链霉菌中类胡萝卜素生物合成的 sigmaB 样因子。
DOI：
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发表时间：
2001
影响因子：
1.2
通讯作者：
S. Horinouchi
中科院分区：
文献类型：
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作者：
H. Lee;Y. Ohnishi;S. Horinouchi
用高拷贝数质粒和灰色链霉菌IFO 13350进行的自克隆实验导致了一个11 kb的DNA片段的克隆，该片段赋予宿主产生黄色色素。克隆的片段包含一个类胡萝卜素生物合成基因簇，其中两个多顺反子crtE（编码香叶基香叶基焦磷酸合成酶）-crtI（八氢番茄红素脱氢酶）-crtB（八氢番茄红素合成酶）-crtV（功能未知的甲基转移酶样蛋白）和crtY（番茄红素环化酶）-crtT（功能未知的甲基转移酶样蛋白）-crtU（β-胡萝卜素脱氢酶）以会聚的方式存在。由于菌株IFO 13350不产生可检测量的类胡萝卜素，因此crt基因簇拷贝数的增加导致以可检测水平产生类胡萝卜素。过表达来自Streptomycessetonii的应激反应sigmaB样蛋白CrtS也激活了S.灰色并赋予色素沉着。在S. griseus，这是由计算机辅助同源搜索预测，引起胡萝卜素的产生相同程度的CrtS的S。setonii，表明两种sigmaB样蛋白在功能上相同。S.由于S中sigmaCrtS的过表达，含有在高拷贝数质粒上的强启动子控制下的crtS的灰色酵母是由于crt基因转录的激活而产生的。griseus导致crtE和crtY前面的启动子的转录激活。S1核酸酶图谱显示crtS本身在实验室条件下以低水平转录，这可能是无法检测到类胡萝卜素产生的原因。crt基因被认为位于非常接近线性染色体的一端，因为它们在两端都有大的缺失的突变体HH1中完全缺失。S. crt的基因组织。griseus与S. coelicolorA3（2），其中crt基因组位于染色体的一端。
Self-cloning experiments with a high-copy-number plasmid and Streptomyces griseus IFO13350 led to the cloning of a 11-kb DNA fragment that conferred yellow pigment production on the host. The cloned fragment contained a gene cluster for carotenoid biosynthesis, in which two polycistrons, crtE (encoding geranylgeranyl pyrophosphate synthase)-crtI (phytoene dehydrogenase)-crtB (phytoene synthase)-crtV (functionally unknown methyltransferase-like protein) and crtY (lycopene cyclase)-crtT (functionally unknown methyltransferase-like protein)-crtU (beta-carotene dehydrogenase), were present in a convergent way. Since strain IFO13350 produced no detectable amount of carotenoids, an increase in the copy number of the crt gene cluster led to production of carotenoids at a detectable level. Overexpression of the stress-responsive sigmaB-like protein CrtS from Streptomyces setonii also activated the cryptic crt genes in S. griseus and conferred pigmentation. A CrtS homologue (sigmaCrtS) in S. griseus, which was predicted by a computer-aided homology search, caused carotenogenesis to the same extent as CrtS of S. setonii, indicating that the two sigmaB-like proteins were functionally the same. Yellow pigment production by S. griseus containing crtS under the control of a strong promoter on a high-copy-number plasmid resulted from activation of transcription of the crt genes, because overexpression of sigmaCrtS in S. griseus led to transcriptional activation of the promoters in front of crtE and crtY. S1 nuclease mapping showed that crtS itself was transcribed at a low level under the laboratory conditions, which may account for undetectable production of carotenoids. The crt genes were suggested to locate very near one end of the linear chromosome, since they were completely deleted in mutant HH1 having large deletions at both ends. The gene organization of crt in S. griseus is similar to that in S. coelicolor A3(2) where the whole crt gene set is near one end of the chromosome.