Understanding the P‐Cluster of Vanadium Nitrogenase: an EPR and XAS Study of the Holo vs. Apo Forms of the Enzyme
Year: 2024
Type: article
Abstract: The catalytic moiety of nitrogenases contains two complex metalloclusters: The M‐cluster (also called cofactor), where the catalytic reduction of substrates takes place, and the [Fe8S7] P‐cluster responsible for electron transfer. Due to discrepancies between crystallography and EPR spectroscopy, the exact structure of the P‐cluster in the VFe protein remains a topic of debate. Herein, we use an apo‐form of VFe (which retains the P‐cluster but lacks the FeVco) to study the VFe P‐cluster. SDS‐PAGE and NativePAGE showed a heterogeneous composition of the VFe and the apo‐VFe samples with the presence of α1β2δ2 and α1β2 complexes. The parallel mode EPR measurements of IDS oxidized MoFe, apo‐MoFe, and VFe samples reveal a signal at g=12 associated with the two‐electron oxidized state of the P‐cluster (P2+) for all three samples, albeit with different intensities. In contrast, no P2+ was observed for IDS oxidized apo‐VFe. Additionally, comparisons between apo‐MoFe, apo‐VFe and the model complex (NBu4)2[Fe4S4(SPh)4] via EXAFS measurements showed that apo‐VFe does not contain a fully formed [Fe8S7] P‐cluster, but rather is comprised of fragmented iron‐sulfur clusters. Our results point to a possible variation in the structure of the P‐cluster in the different forms of the nitrogenase.
Source: ChemBioChem
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,220
OpenAlex ID: W4404422484