He B, Zalkin H
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907.
J Bacteriol. 1994 Feb;176(4):1009-13. doi: 10.1128/jb.176.4.1009-1013.1994.
Escherichia coli purA encodes adenylosuccinate synthetase, one of two enzymes required for synthesis of AMP from IMP. purA is subject to two- to threefold regulation by purR and about twofold regulation by a purR-independent mechanism. The 5'-flanking region of purA confers purR-dependent transcriptional regulation of purA but not the purR-independent regulation. Two operator sites in the 5'-flanking region which bind purine repressor in vitro and are required for in vivo regulation were identified. The purR-independent regulation may be posttranscriptional. It is now established that all transcription units involved in de novo synthesis of purine nucleotides, nine pur operons, as well as purR itself and guaBA, are subject to purR control.
大肠杆菌的purA基因编码腺苷酸琥珀酸合成酶，这是从肌苷酸合成AMP所需的两种酶之一。purA受到purR的两到三倍调节，并受到一种不依赖purR的机制的约两倍调节。purA的5'侧翼区域赋予purA依赖于purR的转录调控，但不赋予不依赖purR的调控。在5'侧翼区域中鉴定出两个体外结合嘌呤阻遏物且体内调控所必需的操纵子位点。不依赖purR的调控可能是转录后调控。现已确定，参与嘌呤核苷酸从头合成的所有转录单位，九个嘌呤操纵子，以及purR本身和guaBA，都受purR控制。
