Walter S, Schrempf H
Universität Osnabrück, Germany.
Mol Gen Genet. 1996 May 23;251(2):186-95. doi: 10.1007/BF02172917.
The Streptomyces reticuli cellulase (Cell, Avicelase) hydrolyzes crystalline cellulose (Avicel) efficiently to cellobiose. The synthesis of the enzyme is induced by Avicel and repressed by glucose. DNA-binding proteins were purified from induced S. reticuli mycelia by affinity chromatography using the upstream region of the cell gene linked to Sepharose. The enriched protein(s) provoked a gel electrophoresis mobility shift of the upstream region, irrespective of the presence or absence of a 14-bp palindromic sequence, and enhanced the transcription of the cell gene by the S. reticuli RNA polymerase in vitro. The binding site (GTGACTGAGCGCCG) for the protein(s) was located in the vicinity of a DNA bend upstream of the transcriptional start site. Results of physiological studies, deletion and gel-shift analyses lead to the conclusion that a 14-bp palindrome (TGGGAGCGCTCCCA)--situated between the transcriptional start site and the structure gene--is the operator for a repressor protein. The data presented suggest that the two identified cis-acting elements, in cooperation with an activator and a repressor, mediate regulation of cell transcription.
网状链霉菌纤维素酶（Cell，微晶纤维素酶）可有效地将结晶纤维素（微晶纤维素）水解为纤维二糖。该酶的合成由微晶纤维素诱导，而被葡萄糖抑制。通过使用与琼脂糖凝胶相连的cell基因上游区域，通过亲和色谱法从诱导的网状链霉菌菌丝体中纯化DNA结合蛋白。无论是否存在14bp的回文序列，富集的蛋白质都会引起上游区域的凝胶电泳迁移率变化，并在体外增强网状链霉菌RNA聚合酶对cell基因的转录。该蛋白质的结合位点（GTGACTGAGCGCCG）位于转录起始位点上游的DNA弯曲附近。生理学研究、缺失和凝胶迁移分析结果得出结论，位于转录起始位点和结构基因之间的14bp回文序列（TGGGAGCGCTCCCA）是阻遏蛋白的操纵子。所呈现的数据表明，两个已鉴定的顺式作用元件与激活剂和阻遏剂协同作用，介导cell转录的调控。
