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Publication Abstract from PubMed

The noncanonical amino acid, para-cyanophenylalanine (CNF), when incorporated into metalloproteins, functions as an infrared spectroscopic probe for the redox state of iron-sulfur clusters, offering a strategy for determining electron occupancy in the electron transport chains of complex metalloenzymes. A redshift of approximately 1-2 cm(-1) in the nitrile (NC) stretching frequency is observed, following reduction of spinach ferredoxin modified to contain CNF close to its [2Fe-2S] center, and this shift is reversed on re-oxidation. We extend this to CNF positioned near to the proximal [4Fe-4S] cluster of the [FeFe] hydrogenase from Desulfovibrio desulfuricans. In combination with a distal [4Fe-4S] cluster and the [4Fe-4S] cluster of the active site 'H-cluster' ([4Fe-4S](H)), the proximal cluster forms an electron relay connecting the active site to the surface of the protein. Again, a reversible shift in wavenumber for CNF is observed, following cluster reduction in either apo-protein (containing the iron-sulfur clusters but lacking the active site) or holo-protein with intact active site, demonstrating the general applicability of this approach to studying complex metalloenzymes.

Cyanophenylalanine as an Infrared Probe for Iron-Sulfur Cluster Redox State in Multicenter Metalloenzymes.,Duan Z, Wei J, Carr SB, Ramirez M, Evans RM, Ash PA, Rodriguez-Macia P, Sachdeva A, Vincent KA Chembiochem. 2025 May 10:e2500251. doi: 10.1002/cbic.202500251. PMID:40347495^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.