创新霉素对其大肠杆菌抗性变株色氨酸合成途径酶合成的促进作用

测定创新霉素(CXM)及其类似物对大肠杆菌色氨酸操纵子表达的影响。结果发现,CXM和L-色氨酸(L-trp)对CXM敏感菌表现为阻遏作用,吲哚丙酸(IPA)则具有去阻遏作用;对CXM抗性变株,CXM与IPA均表现为去阻遏作用,L-trp不具阻遏作用,但可抵消CXM和IPA的去阻遏作用。提示阻遏蛋白和L-trp及其类以物至少有阻遏和去阻遏两个结合部位,CXM可以和这两个部位结合,在敏感菌中显示阻遏作用;在抗性变株中阻遏蛋白的阻遏部应结构改变,CXM显示去阻遏作用。

Enhancing Effect of Chuangxinmycin on Synthesis of Enzymes in Tryptophan Synthesis Pathway of Chuangxinmycin-Resistant Mutant Strain of E. coli

Chuangxtnmycin (CXM) and L-trp cause repression of trp-operon in wild strain of E. coli and indolepropanic acid (IPA) causes derepression of this strain. In CXM-resistant mutant strain, CXM and IPA both cause derepression,and interaction of CXM and IPA is competitive. However, L-trp results in neither repression nor derepression in the mutant, but it can counteract the activity of CXM or IPA. These results suggest that there are repression and derepression sites on repressor of E. coli. CXM can bind to both sites, but mainly to repression site. The structure of repression site of the CXM-resistant mutant is altered, so that CXM can not bind to the repression site and binds mainly to the derepression site, thus leading to the derepression of trp-operon.