ChlR is a MarR-type transcriptional regulator that activates the transcription of the chlAII-ho2-hemN operon in response to low oxygen conditions in the cyanobacterium Synechocystis sp. PCC 6803. Upon exposure to low oxygen conditions, ChlR activates transcription of the operon that encodes enzymes critical to tetrapyrrole biosynthesis under low oxygen conditions. We previously identified a super-activator variant, D35H, of ChlR that constitutively activates transcription of the operon. To gain insight into the low-oxygen induced activation of ChlR, we obtained eight additional super-activator variants of ChlR including D35H from pseudorevertants of a chlAI-disrupted mutant. Most substitutions were located in the N-terminal region of ChlR. Mapping of the substituted amino acid residues provided valuable structural insights that uncovered the activation mechanism of ChlR.

中文翻译：

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蓝细菌转录调节因子ChlR的超级活化剂变体，在低氧条件下对四吡咯生物合成至关重要。

ChlR是一种MarR型转录调节因子，可响应蓝藻集胞藻属sp。中的低氧条件，激活chlAII-ho2-hemN操纵子的转录。PCC6803。暴露于低氧条件下，ChlR激活操纵子的转录，该操纵子编码在低氧条件下对四吡咯生物合成至关重要的酶。我们以前鉴定了ChlR的超级激活子变体D35H，其组成性激活操纵子的转录。为了深入了解低氧诱导的ChlR激活，我们从chlAI破坏突变体的假回复物中获得了ChlR的八个其他超级激活剂变体，包括D35H。大多数取代位于ChlR的N端区域。