He B, Smith J M, Zalkin H
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907.
J Bacteriol. 1992 Jan;174(1):130-6. doi: 10.1128/jb.174.1.130-136.1992.
Escherichia coli purB encodes adenylosuccinate lyase (ASL), the enzyme that catalyzes step 8 in the pathway for de novo synthesis of IMP and also the final reaction in the two-step sequence from IMP to AMP. Gene purB was cloned and found to encode an ASL protein of 435 amino acids having a calculated molecular weight of 49,225. E. coli ASL is homologous to the corresponding enzymes from Bacillus subtilis and chickens and also to fumarase from B. subtilis. Gene phoP is 232 bp downstream of purB. Gene purB is regulated threefold by the purine pool and purR. Transcriptional regulation of purB involves binding of the purine repressor to the 16-bp conserved pur regulon operator. The purB operator is 224 bp downstream of the transcription start site and overlaps codons 62 to 67 in the protein-coding sequence.
大肠杆菌的purB基因编码腺苷酸琥珀酸裂解酶（ASL），该酶催化肌苷酸（IMP）从头合成途径中的第8步反应，也是从IMP到AMP两步反应序列中的最后一步反应。purB基因被克隆出来，发现它编码一个由435个氨基酸组成的ASL蛋白，计算分子量为49225。大肠杆菌ASL与枯草芽孢杆菌和鸡的相应酶同源，也与枯草芽孢杆菌的延胡索酸酶同源。phoP基因位于purB下游232 bp处。purB基因受嘌呤库和purR的三倍调节。purB的转录调控涉及嘌呤阻遏物与16 bp保守的嘌呤操纵子的结合。purB操纵子位于转录起始位点下游224 bp处，与蛋白质编码序列中的第62至67密码子重叠。
