Molecular modeling investigation of proton coupling in XylE

Abstract

Sugar transporters are major facilitator superfamily (MFS) members that play a fundamental role in cell biology: they take up energy into cells in the form of glucose and other hexoses using a rocker-switch alternating access mechanism of transport. XylE is an Escherichia coli homolog that has been often used as a model system to study the molecular basis for sugar transport. In contrast to most known GLUTs, sugar-transport by XylE is proton-coupled. Previous studies have shown that substitution of a single aspartate residue (D27) in TM1 with an asparagine converts XylE into a passive transporter.