title: Regulation of Escherichia coli IscS desulfurase activity by ferrous iron and cysteine.
abstract: IscS plays a principal role in the synthesis of sulfur-containing biomolecules. It is known that the expression of iscS can be negatively regulated by IscR, the first gene product of iscRSUA-hscBA-fdx. What governs the regulation of cysteine desulfurase activity, however, is unknown. Here, we report that IscS from Escherichia coli is able to bind iron with an association constant of 1.6x10(17)M(-1) to form an IscS-iron complex. IscS is also capable of binding both iron and sulfide to form an IscS-iron-sulfide complex with a higher affinity. The desulfurase activity is gradually inhibited as the amount of iron and sulfide bound to IscS increases. When 2Fe-2S binds IscS, about 20% of the activity is inhibited; when 8Fe-8S adheres to IscS, about 70% of the activity is inhibited. Thus, the cell is able to modulate its desulfurase activity with the formation of an IscS-iron-sulfide complex.
authors.affiliation: College of Life Sciences, Zhejiang University, 388 Yuhangtang Road, Hangzhou 310058, China. wugenfu@zju.edu.cn
authors.forename: Genfu
authors.initials: G
authors.lastname: Wu
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.forename: Xuechang
authors.initials: X
authors.lastname: Wu
mesh_terms: D013437:Carbon-Sulfur Lyases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013440:Sulfides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D013440:Sulfides; D013437:Carbon-Sulfur Lyases; C080546:cysteine desulfurase; D003545:Cysteine