A Moessbauer analysis of the low-potential iron-sulfur center in photosystem I: Spectroscopic evidence that F sub x is a (4Fe-4S) cluster

• Published in: Biochemistry (Easton) Vol. 28:23
• Main Authors: Petrouleas, V., Brand, J.J., Parrett, K.G., Golbeck, J.H.
• Format: Journal Article
• Language: English
• Published: United States 14-11-1989
• Subjects: BASIC BIOLOGICAL SCIENCES; CARBOXYLIC ACIDS; CHEMICAL REACTIONS; CHEMICAL SHIFT; CHLOROPHYLL; COMPLEXES; CYANOBACTERIA; ELECTRON SPIN RESONANCE; EVEN-ODD NUCLEI; HETEROCYCLIC ACIDS; HETEROCYCLIC COMPOUNDS; INTERMEDIATE MASS NUCLEI; IRON 57; IRON COMPLEXES; IRON ISOTOPES; ISOTOPE APPLICATIONS; ISOTOPES; MAGNETIC RESONANCE; MICROORGANISMS; NUCLEI; ORGANIC ACIDS; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; OXIDATION; PHOTOSYNTHETIC REACTION CENTERS; PHYTOCHROMES; PIGMENTS; PORPHYRINS; PROTEINS; RESONANCE; STABLE ISOTOPES; SULFUR COMPLEXES; TRACER TECHNIQUES; TRANSITION ELEMENT COMPLEXES 550201 > Biochemistry > Tracer Techniques
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00449a004

The authors report the results of a Moessbauer study of the low-potential iron-sulfur cluster F{sub X} in the Photosystem I core protein of Synechococcus 6301. The Moessbauer spectrum of F{sub X} in the oxidized state shows an isomer shift of 0.42 mm/s, which is in good agreement with the 0.43 mm/s isomer shift found in (4Fe-4S) proteins but not with the isomer shift of 0.26 mm/s found in (2Fe-2S) proteins. In the reduced state the spectrum is asymmetrically broadened at 80 K, indicating the presence of two very closely spaced doublets with an average isomer shift of 0.55 mm/s, which is also in agreement with (4Fe-4S) proteins. At 4.2 K, the spectrum exhibits broadening and magnetic splitting similar to what is observed for (4Fe-4S) proteins and quite unlike (2Fe-2S) proteins. Given the assumption that the iron atoms of F{sub X} are tetrahedrally coordinated with sulfur ligands, the data strongly support the assignment of F{sub X} as a (4Fe-4S) cluster.