A, SDS-polyacrylamide gel of the purified ribose transporter complexes (cofactors or substrates indicated in parentheses): RbsA, 55 kDa (lane 1); RbsB, 30 kDa (lane 2); His-RbsC, 33 kDa (lane 3); RbsAC (lane 4; Mg-ATP-VO4); RbsABC (lane 5; Mg-ATP-VO4); RbsBC (lane 6; none); molecular mass marker (lane 7; all values in kDa). B, SDS-polyacrylamide gel of ribose transporter complex purified in the presence of 1 mm each of Mg2+, ATP, VO4, and ribose. C, SDS-polyacrylamide gel of ribose transporter complex purified in the presence of 1 mm ribose alone.