Mycobacterium tuberculosis cAMP receptor protein (Rv3676) differs from the Escherichia coli paradigm in its cAMP binding and DNA binding properties and transcription activation properties.
Mycobacterium tuberculosis cAMP receptor protein (Rv3676) differs from the Escherichia coli paradigm in its cAMP binding and DNA binding properties and transcription activation properties.
复制标题
结核分枝杆菌 cAMP 受体蛋白 (Rv3676) 与大肠杆菌范例的不同之处在于其 cAMP 结合和 DNA 结合特性以及转录激活特性。
DOI：
10.1074/jbc.m109.047720
复制
发表时间：
2010-03-05
期刊：
影响因子：
--
通讯作者：
Green J
中科院分区：
文献类型：
--
作者：
Stapleton M;Haq I;Hunt DM;Arnvig KB;Artymiuk PJ;Buxton RS;Green J
病原体结核分枝杆菌在感染巨噬细胞时产生cAMP的爆发。细菌环腺苷酸受体蛋白（CRP）是一种转录因子，当cAMP浓度增加时，CRP通过与靶启动子结合来响应cAMP。Rv 3676（CRPMt）是一种CRP家族蛋白，调节可能参与M的基因（rpfA和whiB 1）表达。结核病持续存在和/或从休眠状态出现。在这里，CRPMt同源二聚体显示在非相互作用位点结合两个cAMP分子（每个原聚体一个）。此外，CRPMt的cAMP结合相对较弱，熵驱动，导致DNA结合相对较小的增强。在whiB 1启动子（PwhiB 1）上鉴定出串联的CRPMT结合位点（CRP 1位于-58.5，CRP 2位于-37.5）。体外转录反应表明，CRP 1是一个激活位点，CRP 2，这是只占用在cAMP的存在下，或在高浓度CRPMt在cAMP的情况下，是一个阻遏位点。CRPMt与CRP 1的结合对于开放复合物的形成不是必需的，但对于转录激活是必需的。因此，这些数据表明，结合CRPMt的PwhiB 1 CRP 1网站激活转录后的步骤开放复合物的形成。相反，高cAMP浓度允许CRP 1和CRP 2位点的占用，导致开放复合物形成的抑制。因此，M.与大肠杆菌CRP范例相比，结核病CRP已经进化出几个不同的特征，以允许其在高浓度cAMP的背景下调节基因表达。
The pathogen Mycobacterium tuberculosis produces a burst of cAMP upon infection of macrophages. Bacterial cyclic AMP receptor proteins (CRP) are transcription factors that respond to cAMP by binding at target promoters when cAMP concentrations increase. Rv3676 (CRPMt) is a CRP family protein that regulates expression of genes (rpfA and whiB1) that are potentially involved in M. tuberculosis persistence and/or emergence from the dormant state. Here, the CRPMt homodimer is shown to bind two molecules of cAMP (one per protomer) at noninteracting sites. Furthermore, cAMP binding by CRPMt was relatively weak, entropy driven, and resulted in a relatively small enhancement in DNA binding. Tandem CRPMt-binding sites (CRP1 at −58.5 and CRP2 at −37.5) were identified at the whiB1 promoter (PwhiB1). In vitro transcription reactions showed that CRP1 is an activating site and that CRP2, which was only occupied in the presence of cAMP or at high CRPMt concentrations in the absence of cAMP, is a repressing site. Binding of CRPMt to CRP1 was not essential for open complex formation but was required for transcription activation. Thus, these data suggest that binding of CRPMt to the PwhiB1 CRP1 site activates transcription at a step after open complex formation. In contrast, high cAMP concentrations allowed occupation of both CRP1 and CRP2 sites, resulting in inhibition of open complex formation. Thus, M. tuberculosis CRP has evolved several distinct characteristics, compared with the Escherichia coli CRP paradigm, to allow it to regulate gene expression against a background of high concentrations of cAMP.