Joshi M, Dikshit K L
Institute of Microbial Technology, Chandigarh, India.
Biochem Biophys Res Commun. 1994 Jul 15;202(1):535-42. doi: 10.1006/bbrc.1994.1961.
Vitreoscilla globin (vgb) gene, encoding for Vitreoscilla haemoglobin (VtHb) has been cloned and functionally expressed in heterologous bacterial hosts. Analysis of vgb gene expression and the study on vgb-xylE transcriptional fusion revealed that vgb promoter is preferentially activated in response to oxygen limitation in Vitreoscilla and other heterologous bacterial hosts. Microaerobic mode of induction in various hosts, provided evidence for a common regulatory factor involved in activation of vgb promoter under hypoxic condition. Primary structure analysis of vgb upstream regulatory region indicated the presence of a possible binding site for the transcriptional activator, FNR. Further, the E.coli mutant lacking fnr gene product was not able to activate vgb promoter under microaerobic condition, suggesting the involvement of FNR or FNR-like proteins in modulating its activity. The possibility of a second level of control by CRP is also indicated. Oxygen responsive nature and regulatory characteristics of vgb promoter offers a novel system for the expression of gene in heterologous bacterial hosts in an oxygen dependent manner.
编码透明颤菌血红蛋白（VtHb）的透明颤菌球蛋白（vgb）基因已被克隆，并在异源细菌宿主中实现了功能表达。对vgb基因表达的分析以及对vgb-xylE转录融合的研究表明，vgb启动子在透明颤菌和其他异源细菌宿主中优先响应氧限制而被激活。在各种宿主中的微需氧诱导模式，为缺氧条件下参与vgb启动子激活的共同调节因子提供了证据。vgb上游调控区域的一级结构分析表明存在转录激活因子FNR的可能结合位点。此外，缺乏fnr基因产物的大肠杆菌突变体在微需氧条件下无法激活vgb启动子，这表明FNR或FNR样蛋白参与调节其活性。同时也表明了CRP进行二级调控的可能性。vgb启动子的氧响应特性和调控特征为以氧依赖方式在异源细菌宿主中表达基因提供了一个新系统。
