The crystal structure of a sodium galactose transporter reveals mechanistic insights into Na+/sugar symport.
Membrane transporters that use energy stored in sodium gradients to drive nutrients into cells constitute a major class of proteins. We report the crystal structure of a member of the solute sodium symporters (SSS), the Vibrio parahaemolyticus sodium/galactose symporter (vSGLT). The approximately 3.0 angstrom structure contains 14 transmembrane (TM) helices in an inward-facing conformation with a core structure of inverted repeats of 5 TM helices (TM2 to TM6 and TM7 to TM11). Galactose is bound in the center of the core, occluded from the outside solutions by hydrophobic residues. Surprisingly, the architecture of the core is similar to that of the leucine transporter (LeuT) from a different gene family. Modeling the outward-facing conformation based on the LeuT structure, in conjunction with biophysical data, provides insight into structural rearrangements for active transport.
Faham
Salem
S
Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095-1751, USA.
Watanabe
Akira
A
Besserer
Gabriel Mercado
GM
Cascio
Duilio
D
Specht
Alexandre
A
Hirayama
Bruce A
BA
Wright
Ernest M
EM
Abramson
Jeff
J
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D001692:Biological Transport; D018360:Crystallography, X-Ray; D019281:Dimerization; D005690:Galactose / Q000737:chemistry / Q000378:metabolism*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012964:Sodium / Q000737:chemistry / Q000378:metabolism*; D051247:Sodium-Glucose Transport Proteins / Q000737:chemistry* / Q000378:metabolism; D014736:Vibrio parahaemolyticus / Q000737:chemistry* / Q000378:metabolism
D001426:Bacterial Proteins; D008051:Lipid Bilayers; D051247:Sodium-Glucose Transport Proteins; C099811:sodium glucose symporter, Vibrio parahaemolyticus; D012964:Sodium; D005690:Galactose