Figure 5. MCT expression and localization in WT and mutant LX-2 cell lines.
(A) Western blotting of protein signals in LX-2 whole cell lysates (L), as well as cytosolic soluble (S) and membrane (M) fractions separated by ultracentrifugation. The control cell surface protein integrin αVβ3 exhibits preferential localization to M over S fractions. MCT1 and MCT4 signals are consistently and preferentially located in M over S fractions. (B) MCT1 and MCT4 signals in the lysate or membrane fractions were normalized to stain-free gel image intensities (Fig. S5). (C) Sequence alignment of Bsg and Nptn transmembrane regions. Sequence mismatches detected by ClustalW algorithm are highlighted in red. Homology of the transmembrane regions putatively responsible for MCT binding was 60%, whereas overall protein homology was 39%. Residues at both the N- and C- termini regions of the transmembrane domain are mismatched (red), potentially preventing interactions with MCT1 and MCT4.