The cAMP receptor protein CRP can function as an osmoregulator of transcription in Escherichia coli
The cAMP receptor protein CRP can function as an osmoregulator of transcription in Escherichia coli
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DOI：
10.1101/gad.13.23.3081
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发表时间：
1999-12-01
影响因子：
10.5
通讯作者：
Johnson, RC
中科院分区：
文献类型：
--
作者：
Landis, L;Xu, JM;Johnson, RC
大肠杆菌proP基因的pi启动子的转录，该基因编码一种抗氧化剂保护剂的转运蛋白，强烈诱导转移到高渗介质。不像大多数其他受调节的启动子，诱导发生一段短暂的时间，对应于细胞内的K+谷氨酸盐与谷氨酸保护化合物的替代。proP转录的这种爆发与cAMP受体蛋白CRP与proP pi启动子内的位点的渗透压依赖性结合相关。我们表明，CRP-cAMP的功能作为一个敏感的阻遏物的proP PI转录在体外。CRP与proP启动子在体内的结合在高渗转变后瞬时不稳定，其动力学对应于转录的去阻遏，而Fis和Lac阻遏物结合不敏感。CRP* 突变体对proP P1转录的类似渗透调节意味着cAMP的结合不负责CRP活性的异常渗透敏感性。CRP活性的渗透调节不限于proP。CRP对lac启动子的激活在渗透上移后也被短暂抑制，CRP与gal Delta 4 P1启动子的结合也是如此。这些发现表明，CRP的功能在某些情况下，以调节基因表达的渗透变化，除了其在分解代谢物控制的作用。
Transcription of the pi promoter of the Escherichia coli proP gene, which encodes a transporter of osmoprotectants, is strongly induced by a shift to hyperosmotic media. Unlike most other osmotically regulated promoters, the induction occurs for a brief period of time, corresponding to the replacement of intracellular K+ glutamate with osmoprotecting compounds. This burst of proP transcription is correlated with the osmolarity-dependent binding of the cAMP receptor protein CRP to a site within the proP pi promoter. We show that CRP-cAMP functions as an osmotically sensitive repressor of proP pi transcription in vitro. Binding of CRP to the proP promoter in vivo is transiently destabilized after a hyperosmotic shift with kinetics that correspond to the derepression of transcription, whereas Fis and Lac repressor binding is not osmotically sensitive, Similar osmotic regulation of proP P1 transcription by the CRP* mutant implies that binding of cAMP is not responsible for the unusual osmotic sensitivity of CRP activity. Osmotic regulation of CRP activity is not limited to proP. Activation of the lac promoter by CRP is also transiently inhibited after an osmotic upshift, as is the binding of CRP to the gal Delta 4 P1 promoter. These findings suggest that CRP functions in certain contexts to regulate gene expression in response to osmotic changes, in addition to its role in catabolite control.