Localization of MIPs in membrane fractions separated by continuous Suc density gradient centrifugation. A, Suc concentrations in collected fractions show linearity of the gradient. B, Membrane protein profile from M. crystallinum cell suspensions of selected fractions on Coomassie Blue-stained gels (12.5% [w/v] acrylamide) and immunological detection in the respective fractions of (from top to bottom) P-ATPase, V-ATPase, V-PPase, MIP-A, MIP-B, and MIP-F (in membrane protein isolated from cell suspensions) and MIP-C (in membrane protein isolated from roots). Molecular masses of bands are indicated.