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A synthetic analogue for the active site of plant-type ferredoxin: two different coordination isomers by a four-Cys-containing -peptide
- Ueyama, N., Ueno, S., Nakamura, A., Wada, K., Matsubara, H., Kumagai, S., Sakakibara, S., Tsukihara, T.
- Biopolymers 1992 v.32 no.11 pp. 1535-1544
- cysteine, synthetic peptides, isomers, amino acid sequences, sulfur, redox potential, nuclear magnetic resonance spectroscopy, binding sites
- The (Fe2S2)2+ complex of an artificial 20-peptide ligand Ac-Pro-Tyr-Ser-Cys-Arg-Ala-Gly-Ala-Cys-Ser-Thr-Cys-Ala-Gly-Pro-Leu-Leu-Thr -Cys-Val-NH2, containing an invariant Cys-A-B-C-D-Cys-X-Y-Cys (A, B, C, D, X, Y = amino acid residues) fragment of plant-type ferredoxins was synthesized by a ligand exchange method with [Fe2S2 (S-t-Bu)4]2(-). 1H-nmr spectroscopic and electrochemical data of the complex indicate the presence of two coordination isomers. One of them having a Cys-X-Y-Cys bridging coordination to the two Fe(III) ions, has the (Fe2S2)2+ core environment similar to those of the denatured plant-type ferredoxins and exhibits a positive shifted redox potential at -0.64 V vs saturated colonel electrode (SCE) in N,N-dimethylformamide (DMF). Another isomer with the Cys-A-B-C-D-Cys bridging coordination shows a negative redox potential at -0.96 V vs SCE in DMF.