Banerjee-Bhatnagar N
International Centre for Genetic Engineering and Biotechnology, New Delhi, 110067, India.
Biochem Biophys Res Commun. 1998 Nov 18;252(2):402-6. doi: 10.1006/bbrc.1998.9455.
Bacillus thuringiensis subsp. israelensis (Bti) produces Cry IV A protoxin protein as part of the insecticidal crystal toxin during sporulation. This study was conducted with the objective of identifying environmental signals which regulate toxin synthesis by Bti. Glucose was found to repress Cry IV A toxin induction at the mRNA level. The repressive effect of glucose was dependent on a phosphorylation step since protein kinase inhibitor calphostin c relieved the 130-kD protoxin synthesis at both the mRNA and protein level. Phosphorylation of HPr, the phosphocarrier protein of the phosphotransferase system, occurred during glucose repression of Cry IV A toxin synthesis in Bti cells was seen by Western blotting with anti-phosphoserine antibody and rabbit anti-HPr serum. Phosphorylation of HPr in vivo as well as in the in vitro assay was inhibited by calphostin c, a specific inhibitor of serine/threonine kinase. Calphostin c had no effect on sporulation efficiency of Bti cells.
苏云金芽孢杆菌以色列亚种（Bti）在芽孢形成过程中产生Cry IV A原毒素蛋白，作为杀虫晶体毒素的一部分。本研究旨在确定调节Bti毒素合成的环境信号。发现葡萄糖在mRNA水平上抑制Cry IV A毒素的诱导。葡萄糖的抑制作用依赖于磷酸化步骤，因为蛋白激酶抑制剂钙泊三醇c在mRNA和蛋白质水平上均解除了130-kD原毒素的合成。通过用抗磷酸丝氨酸抗体和兔抗HPr血清进行蛋白质印迹分析，发现在Bti细胞中葡萄糖抑制Cry IV A毒素合成期间，磷酸转移酶系统的磷酸载体蛋白HPr发生了磷酸化。钙泊三醇c是丝氨酸/苏氨酸激酶的特异性抑制剂，它在体内和体外试验中均抑制了HPr的磷酸化。钙泊三醇c对Bti细胞的芽孢形成效率没有影响。
