TY  - JOUR
A1  - Thummer, Robert
A1  - Klimmek, Oliver
A1  - Schmitz, Ruth A.
T1  - Biochemical studies of Klebsiella pneumoniae NifL reduction using reconstituted partial anaerobic respiratory chains of Wolinella succinogenes
T2  - Journal of biological chemistry
N2  - In the diazotroph Klebsiella pneumoniae the flavoprotein NifL inhibits the activity of the nif-specific transcriptional activator NifA in response to molecular oxygen and combined nitrogen. Sequestration of reduced NifL to the cytoplasmic membrane under anaerobic and nitrogen-limited conditions impairs inhibition of cytoplasmic NifA by NifL. To analyze whether NifL is reduced by electrons directly derived from the reduced menaquinone pool, we studied NifL reduction using artificial membrane systems containing purified components of the anaerobic respiratory chain of Wolinella succinogenes. In this in vitro assay using proteoliposomes containing purified formate dehydrogenase and purified menaquinone (MK6) or 8-methylmenaquinone (MMK6) from W. succinogenes, reduction of purified NifL was achieved by formate oxidation. Furthermore, the respective reduction rates, which were determined using equal amounts of NifL, have been shown to be directly dependent on the concentration of both formate dehydrogenase and menaquinones incorporated into the proteoliposomes, demonstrating a direct electron transfer from menaquinone to NifL. When purified hydrogenase and MK6 from W. succinogenes were inserted into the proteoliposomes, NifL was reduced with nearly the same rate by hydrogen oxidation. In both cases reduced NifL was found to be highly associated to the proteoliposomes, which is in accordance with our previous findings in vivo. On the bases of these experiments, we propose that the redox state of the menaquinone pool is the redox signal for nif regulation in K. pneumoniae by directly transferring electrons onto NifL under anaerobic conditions.
Y1  - 2021
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/76300
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-763003
SN  - 0021-9258
VL  - 282.2007
IS  - 17
SP  - 12517
EP  - 12526
PB  - American Society for Biochemistry and Molecular Biology Publications
CY  - Bethesda, Md
ER  -