SDS/PAGE analyses of purified recombinant yeast RNR subunits (1–2 μg per lane) isolated from E. coli. Lanes 1 and 8, molecular mass markers (kDa); lane 2, Rnr1p; lane 3, Rnr3p; lane 4, H6Rnr2p; lane 5, Rnr4p; lane 6, H6Rnr2p/Rnr4p complex; lane 7, H6Rnr2p/ΔRnr4p complex.