Fig. 5.
SDS-PAGE of cytochrome f purified from turnip thylakoid membranes (lane A), compared to that of the cytochrome in membranes that were dissolved in SDS and run on the get without prior extraction (lane B). ΔMr = 3,000 between the two bands that correspond to polypeptides with (A) the 252 residue turnip cyt f fragment (arrow) and (B) the complete turnip cyt f polypeptide with 285 residues. The molecular weight of the 252-residue polypeptide is 27,500 including the covalently bound heme. The purification procedure was essentially as described by Gray (1978), except for the use of PMSF (0.5 mM), benzamidine (2 mM), and ε-aminocaproic acid (2 mM) (Martinez et al., 1992, 1993). For electrophoresis, the cytochrome was solubilized in 50 mM Tris-HCl, pH 8.6, 4 M urea, 4% SDS, 10% glycerol, and 5% β-mercaptoethanol, and run with a gel system containing 15% acrylamide (Piccioni et al., 1982).