Association of Fe-S center(s) with the large subunit(s) of photosystem I particles

Treatment of photosystem I particles from spinach (Spinacia oleracea) with dodecyl sulfate destroyed the protein-bound Fe-S centers and converted some of the acid-labile sulfide to zero-valence sulfur which remained covalently bound to the proteins. When the proteins were resolved by gel-permeation chromatography or by polyacrylamide gel electrophoresis in the presence of dodecyl sulfate, a considerable amount of zero-valence sulfur was associated with the large molecular weight polypeptide(s) (63,000 and 59,000). The results strongly suggest that an intact two-peptide P700 chlorophyll a-protein is an Fe-S protein.