Expression of the TM C265S mutant is reduced on the cell surface. (A) Representative TM western blot data from total cell lysates (Total), cytosol, organelle membranes (Organelle), and plasma membrane (Plasma) fractions prepared from nontransfected cells (No) and cells transfected with TM-WT or -C265S mutant (CS) expression vectors. His-tagged TM protein was detected after SDS-PAGE and western blot analysis, with an anti-His tag antibody. The top main band at ∼90 kDa and the bottom one at ∼80 kDa presumably represent the mature glycosylated and unglycosylated forms of TM, respectively. (B) Quantification of TM in plasma membrane fractions of WT or C265S cells (n = 3 experiments; mean ± SD).