Function, Structure, and Evolution of the Major Facilitator Superfamily: The LacY Manifesto
Figure 1
Transport reactions catalyzed by MFS. (a) Schematic illustration of active transports (symport, e.g., LacY, and antiport, e.g., GlpT) and facilitated diffusion (e.g., GLUT1). The red and green arrows indicate the transport directions of substrate and cosubstrate. (b) Uphill substrate (S) accumulation in response to generated by either respiration or ATP hydrolysis by F1FO-ATPase. (c) Uphill transport in response to an inwardly directed downhill lactose gradient (influx). (d) Uphill transport in response to an outwardly directed downhill lactose gradient (efflux). Substrate gradients generate , the polarity of which depends upon the direction of the substrate concentration gradient.
