Cotter P A, Darie S, Gunsalus R P
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024.
FEMS Microbiol Lett. 1992 Dec 15;100(1-3):227-32. doi: 10.1111/j.1574-6968.1992.tb14045.x.
To determine whether the aerobic and anaerobic respiratory pathways of Escherichia coli are regulated in response to iron availability, strains containing lacZ reporter fusions to the cydAB, cyoABCDE, narGHJI, dmsABC and frdABCD operons were grown in medium limited for iron by use of the chelator, 2,2'-dipyridyl. Under anaerobic conditions, expression of the anaerobic respiratory pathway operons, narG-lacZ, dmsA-lacZ and frdA-lacZ, was reduced 14-16 fold when iron was limited. In contrast, expression of the aerobic pathway operons, cyoA-lacZ and cydA-lacZ, was elevated modestly. Iron-dependent transcriptional control of these operons was independent of the fur gene which encodes an iron-and-DNA-binding regulatory protein. The expression of fnr-lacZ was relatively unaffected by iron limitation suggesting that Fnr levels in the cell do not change in response to iron. The above findings suggest that in addition to Fur, some other cellular protein may bind iron for reporting and regulating iron-dependent cell functions.
为了确定大肠杆菌的有氧和无氧呼吸途径是否会根据铁的可利用性进行调节，通过使用螯合剂2,2'-联吡啶，在铁受限的培养基中培养含有与cydAB、cyoABCDE、narGHJI、dmsABC和frdABCD操纵子融合的lacZ报告基因的菌株。在厌氧条件下，当铁受到限制时，厌氧呼吸途径操纵子narG-lacZ、dmsA-lacZ和frdA-lacZ的表达降低了14至16倍。相比之下，有氧途径操纵子cyoA-lacZ和cydA-lacZ的表达适度升高。这些操纵子的铁依赖性转录控制独立于编码铁和DNA结合调节蛋白的fur基因。fnr-lacZ的表达相对不受铁限制的影响，这表明细胞中的Fnr水平不会因铁而改变。上述发现表明，除了Fur之外，一些其他细胞蛋白可能结合铁以报告和调节铁依赖性细胞功能。
