Electrogenic symport of glucose and protons in membrane vesicles of Phanerochaete chrysosporium

The white rot fungus, Phanerochaete chrysosporium, is one of the few organisms with documented ability to degrade lignin. Protoplasts from P. chrysosporium were disrupted by osmotic shock and membrane vesicles were isolated from the cell debris. The vesicles exhibit active glucose transport that is consistent with a glucose/H+ symport mechanism. An artificial gradient of H+ (outside greater than inside) stimulates glucose uptake. Conversely, a glucose gradient (outside greater than inside) results in the accumulation of H+ by the vesicles. Glucose uptake is not stimulated by either a Na+ or a K+ gradient. Furthermore, glucose transport is electrogenic, since glucose uptake may be driven by a membrane potential (negative interior) created by K+ diffusion mediated by valinomycin.