EVIDENCE FOR 2 DIFFERENT RIESKE IRON-SULFUR PROTEINS IN THE CYTOCHROME BF COMPLEX OF SPINACH CHLOROPLAST

Spinach thylakoids, grana vesicles, stroma lamellae vesicles and also isolated cytochrome bf complex, were analysed by two-dimensional polya crylamide gel electrophoresis employing isoelectric focusing in the fi rst dimension and sodium dodecyl-sulfate polyacrylamide gel electropho resis in the second dimension. About 100 thylakoid membrane proteins w ere resolved. In all cases the Rieske FeS protein separated into two p olypeptide spots having the isoelectric points of 5.1 and 5.4, respect ively. The Rieske FeS protein was identified by immunoblot analysis an d by microsequences of the first 23 N-terminal amino acids. The intens ity of the Coomassie brilliant blue stain of the two spots was stronge r for the Rieske FeS protein of the grana vesicles than for that of th e stroma lamellae vesicles.