Structures of the Prokaryotic Galactose Transporter vSGLT and Their Implications on Alternating Access Mechanism in Human SGLT1

Secondary active transporters couple electrochemical energy to the transport of solutes across biological membrane. The sodium solute symporters (SSS) comprise a large family of secondary active transporters fundamental to the homeostasis of a variety of solutes including sugars, inositols, anions, short chain fatty acids, choline, and vitamins. This chapter will explicate the structural framework of the sodium galactose transporter from Vibrio parahaemolyticus (vSGLT) and focus on mechanistic hypothesis drawn from these structures, some of which were directly transferable to the human homologues of vSGLT, which are members of the medically important SLC5 family. Compiling functional, structural, and bioinformatics data generated from these studies and incorporating unique conformations from structurally similar proteins, we propose a modified mechanism for sodium-dependent transport.