Geng Hefang, Jiang Rongrong
School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore, 637459, Singapore.
Appl Microbiol Biotechnol. 2015 Jun;99(11):4533-43. doi: 10.1007/s00253-015-6587-0. Epub 2015 Apr 26.
Cyclic AMP receptor protein (CRP) is one of the seven global regulators in Escherichia coli, which regulates the expression of over 490 genes. It contains a cAMP binding N-terminal domain and a DNA binding C-terminal domain, connected via a short hinge region. Various stress-tolerant E. coli mutants had been obtained through transcriptional engineering of CRP. This review aims to shed some light on the possible mechanism behind these CRP variants, from the change in CRP structure, transcription profile, and DNA binding affinity. The amino acid substitutions are distributed along the protein-certain mutations have shown higher frequency than others, such as T127N and D138Y. β-Galactosidase reporter gene assay revealed that CRP mutants had lower binding affinity with all three classes of CRP-dependent promoters as compared to native CRP, which probably would change cellular transcription profile. Different CRP mutants would induce different cellular transcription profile in E. coli, but there are common genes differentially expressed in these variants, including upregulated gadAB and downregulated nontransporter genes aspA and tnaA, and transporter/poringenes malE, mglB, cstA, and lamB. We believe that transcriptional engineering of CRP can provide an alternative strain engineering method for E. coli and its detailed mechanism may need further investigations.
环磷酸腺苷受体蛋白（CRP）是大肠杆菌中的七种全局调节因子之一，它调控超过490个基因的表达。它包含一个cAMP结合的N端结构域和一个DNA结合的C端结构域，通过一个短的铰链区相连。通过对CRP进行转录工程已获得了各种耐胁迫的大肠杆菌突变体。本综述旨在从CRP结构、转录谱和DNA结合亲和力的变化方面，阐明这些CRP变体背后可能的机制。氨基酸取代沿着蛋白质分布——某些突变的出现频率高于其他突变，如T127N和D138Y。β-半乳糖苷酶报告基因检测显示，与天然CRP相比，CRP突变体与所有三类CRP依赖性启动子的结合亲和力较低，这可能会改变细胞转录谱。不同的CRP突变体在大肠杆菌中会诱导不同的细胞转录谱，但这些变体中存在共同的差异表达基因，包括上调的gadAB和下调的非转运蛋白基因aspA和tnaA，以及转运蛋白/孔蛋白基因malE、mglB、cstA和lamB。我们认为，对CRP进行转录工程可为大肠杆菌提供一种替代的菌株工程方法，其详细机制可能需要进一步研究。
