Expression of Escherichia coli pabA.
Expression of Escherichia coli pabA.
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大肠杆菌pabA的表达。
DOI：
10.1128/jb.173.12.3680-3687.1991
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发表时间：
1991
影响因子：
3.2
通讯作者：
Nichols,BP
中科院分区：
文献类型：
--
作者：
Tran,PV;Nichols,BP
大肠杆菌pabA编码对氨基苯甲酸合酶的谷氨酰胺氨基转移酶亚基。对氨基苯甲酸合酶催化choris酸和谷氨酰胺转化为4-氨基-4-脱氧choris酸，然后通过4-氨基-4-脱氧choris酸裂解酶将其转化为对氨基苯甲酸酯。pabA的5'末端片段先前被证明是从两个不同的启动子转录的，一个靠近pabA编码序列（P1），一个在前面（P2）。然而，pabA-lacZ翻译融合仅由起源于P1的mRNA表达。我们已经确定pabA- lacz染色体融合的表达不受对氨基苯甲酸限制、生长速度、分解代谢抑制、对氨基苯甲酸合成酶亚基过表达或pabA和pabB基因剂量的影响。P2缺乏pabA的表达似乎是由于pabA之前的基因间空间中存在稳定的二级结构，该结构隔离了pabA核糖体结合位点。通过突变破坏二级结构允许P2表达pabA，核糖体翻译到fic-pabA基因间区也是如此。
Escherichia coli pabA encodes the glutamine amidotransferase subunit of p-aminobenzoate synthase. p-Aminobenzoate synthase catalyzes the conversion of chorismate and glutamine to 4-amino-4-deoxychorismate, which is then converted to p-aminobenzoate by a 4-amino-4-deoxychorismate lyase. The 5'-terminal segment of pabA was previously shown to be transcribed from two different promoters, one near the pabA coding sequence (P1) and one preceding fic (P2). However, a pabA-lacZ translational fusion was expressed only from the mRNA originating at P1. We have determined that expression of a pabA-lacZ chromosomal fusion is not changed by p-aminobenzoate limitation, growth rate, catabolite repression, overexpression of either p-aminobenzoate synthase subunit, or gene dosage of pabA and pabB. The lack of pabA expression from P2 appears to be the result of a stable secondary structure in the intergenic space preceding pabA that sequesters the pabA ribosome binding site. Disruption of the secondary structure by mutation allowed expression of pabA from P2, as did translation of ribosomes into the fic-pabA intergenic region.