The differential role of Cys‐421 and Cys‐429 of the Glut1 glucose transporter in transport inhibition by p‐chloromercuribenzenesulfonic acid (pCMBS) or cytochalasin B (CB)

Publisher Website
Google Scholar
Abstract
Cys‐421 and Cys‐429 of Glut1 were replaced by site‐directed mutagenesis in order to investigate their involvement in basal glucose transport and transport inhibition. Neither of the two cysteine residues was essential for basal 2‐deoxy‐D‐glucose uptake in Xenopus oocytes expressing the respective mutant M421 and M429. If applied from the external side, the poorly permeable sulfhydryl‐reactive agent pCMBS inhibited 2‐deoxy‐D‐glucose uptake of Glut1 ‐ and M421‐expressing Xenopus oocytes but failed to affect uptake of the Cys‐429 mutant. This is in agreement with the proposed two‐dimensional model or Glut1 confirming that Cys‐429 is the only residue exposed to the surface of the plasma membrane. The replacement of Cys‐421 at the exofacial end of helix eleven caused a partial protection of 3‐O‐methylglucose transport inhibition by CB; this residue may thus be involved in stabilizing an adjacent local tertiary structure necessary for the full activity of this inhibitor.