TM levels after treatment of cells with epoxomicin. Cells expressing the TM-C265S mutant protein were cultured in the absence or presence of the proteasome inhibitor epoxomicin for 11 hours. TM protein was subsequently detected after separation by SDS-PAGE and western blot analysis with an anti-His tag antibody. Total, cell lysates; Organelle, organelle membranes; Plasma, plasma membranes.