Dataset Information

E.p.r. and magnetic circular dichroism spectroscopic characterization of bacterioferritin from Pseudomonas aeruginosa and Azotobacter vinelandii.

ABSTRACT: The e.p.r. and magnetic circular dichroism (m.c.d.) spectra of bacterioferritin (BFR) extracted from Pseudomonas aeruginosa and Azotobacter vinelandii have been studied over a wide temperature range down to liquid-helium temperature. The e.p.r. spectra show the presence of low-spin Fe3+ haem with g values of 2.86, 2.32, 1.48 (P. aeruginosa) and 2.88, 2.31, 1.46 (A. vinelandii), in both the presence and absence of the BFR core. Together with evidence from the porphyrin-to-Fe3+ charge-transfer band at 2240 and 2270 nm the axial haem ligands are identified as two methionines. The low-temperature m.c.d. spectra in the region 300-1000 nm of P. aeruginosa and A. vinelandii BFR are identical with one another and unaffected by removal of the iron core. Hence it can be concluded that the presence of the iron core has no detectable effect on the electronic states and on the stereochemistry of the haem group. This was unexpected, in view of the observations by Watt, Frankel, Papaefthymiou, Spartalian & Stiefel [(1986) Biochemistry 25, 4330-4336] that the redox potential of the haem group in A. vinelandii BFR shifts from -475 mV to -225 mV on removal of the core. The e.p.r. spectra of holoBFR show a broad symmetrical derivative-shaped band centred at g = 2.0 which decreases in bandwidth as the temperature is raised. This signal is assigned to the uncompensated electron spins of the iron core.

SUBMITTER: Cheesman MR

PROVIDER: S-EPMC1132906 | biostudies-other | 1992 Sep

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:Biological nitrogen fixation, the microbial reduction of atmospheric nitrogen to bioavailable ammonia, represents both a major limitation on biological productivity and a highly desirable engineering target for synthetic biology. However, the engineering of nitrogen fixation requires an integrated understanding of how the gene regulatory dynamics of host diazotrophs respond across sequence-function space of its central catalytic metalloenzyme, nitrogenase. Here, we interrogate this relationship by analyzing the transcriptome of Azotobacter vinelandii engineered with a phylogenetically inferred ancestral nitrogenase protein variant. The engineered strain exhibits reduced cellular nitrogenase activity but recovers wild-type growth rates following an extended lag period. We find that expression of genes within the immediate nitrogen fixation network is resilient to the introduced nitrogenase sequence-level perturbations. Rather the sustained physiological compatibility with the ancestral nitrogenase variant is accompanied by reduced expression of genes that support trace metal and electron resource allocation to nitrogenase. Our results spotlight gene expression changes in cellular processes adjacent to nitrogen fixation as productive engineering considerations to improve compatibility between remodeled nitrogenase proteins and engineered host diazotrophs. IMPORTANCE Azotobacter vinelandii is a key model bacterium for the study of biological nitrogen fixation, an important metabolic process catalyzed by nitrogenase enzymes. Here, we demonstrate that compatibilities between engineered A. vinelandii strains and nitrogenase variants can be modulated at the regulatory level. The engineered strain studied here responds by adjusting the expression of proteins involved in cellular processes adjacent to nitrogen fixation, rather than that of nitrogenase proteins themselves. These insights can inform future strategies to transfer nitrogenase variants to non-native hosts.

Dataset Information

E.p.r. and magnetic circular dichroism spectroscopic characterization of bacterioferritin from Pseudomonas aeruginosa and Azotobacter vinelandii.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure