title: Mechanistic studies on formation of the dinitrosyl iron complex of the [2Fe-2S] cluster of SoxR protein.
abstract: The transcriptional activation of SoxR in Escherichia coli occurs through direct modification of the [2Fe-2S] by nitric oxide (NO) to form a dinitrosyl iron complex (DNIC). Here, we investigated the reactions of NO with [2Fe-2S] clusters of SoxR; the results were compared with those obtained for spinach ferredoxin (Fd). UV-visible absorption and ESR spectra of SoxR upon treatment with an NO donor showed the formation of DNIC of SoxR efficiently, whereas those of Fd exhibited small changes. Upon pulse radiolysis of a deaerated solution of SoxR in the presence of sodium nitrite, a biphasic change in absorption, consisting of a faster phase and a slower phase, was observed. The slower phase fraction was increased with increases in the [NO]/[SoxR] molar ratio, reaching a plateau at ∼2 equivalents of NO. On the basis of these results, we propose that the faster phase corresponds to the reaction of the first NO molecule with [2Fe-2S] of SoxR, followed by the reaction of the second NO molecule. In the reaction of NO with Fd, no slower phase was observed. These results suggest that the reaction of the second equivalent of NO is an important process for the formation of DNIC.
authors.affiliation: The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Mayu
authors.initials: M
authors.lastname: Fujikawa
authors.affiliation: The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan kobayasi@sanken.osaka-u.ac.jp.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kobayashi
authors.affiliation: The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kozawa
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D005288:Ferredoxins / Q000737:chemistry / Q000378:metabolism; D006834:Hydrazines / Q000494:pharmacology; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008956:Models, Chemical; D009569:Nitric Oxide / Q000737:chemistry* / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009589:Nitrogen Oxides / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000528:radiation effects; D012977:Sodium Nitrite / Q000737:chemistry / Q000378:metabolism; D013053:Spectrophotometry; D018724:Spinacia oleracea / Q000378:metabolism; D013455:Sulfur / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism
chemical_list: C115239:3-(2-hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-propanamine; D001426:Bacterial Proteins; D005288:Ferredoxins; D006834:Hydrazines; D007506:Iron-Sulfur Proteins; D020030:Nitric Oxide Donors; D009589:Nitrogen Oxides; D010940:Plant Proteins; D014157:Transcription Factors; C070724:SoxR protein, Bacteria; D009569:Nitric Oxide; C073661:dinitrosyl iron complex; D013455:Sulfur; D007501:Iron; D012977:Sodium Nitrite
keywords: dinitrosyl iron complex; iron–sulfur cluster; nitric oxide; pulse radiolysis; transcription factor