The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)

Sugar binding to Na+/glucose cotransporters is determined by the carboxyl-terminal half of the protein.

d-Glucose is absorbed across the proximal tubule of the kidney by two Na+/glucose cotransporters (SGLT1 and SGLT2). The low affinity SGLT2 is expressed in the S1 and S2 segments, has a Na+:glucose coupling ratio of 1, a K0.5 for sugar of approximately 2 mM, and a K0.5 for Na+ of approximately 1 mM. The high affinity SGLT1, found in the S3 segment, has a coupling ratio of 2, and K0.5 for sugar and Na+ of approximately 0.2 and 5 mM, respectively. We have constructed a chimeric protein consisting of amino acids 1-380 of porcine SGLT2 and amino acids 381-662 of porcine SGLT1. The chimera was expressed in Xenopus oocytes, and steady-state kinetics were characterized by a two-electrode voltage-clamp. The K0.5 for alpha-methyl-d-glucopyranoside (0.2 mM) was similar to that for SGLT1, and like SGLT1 the chimera transported D-galactose and 3-O-methylglucose. In contrast, SGLT2 transports poorly D-galactose and excludes 3-O-methylglucose. The apparent K0.5Na was 3.5 mM (at -150 mV), and the Hill coefficient ranged between 0.8 and 1. 5. We conclude that recognition/transport of organic substrate is mediated by interactions distal to amino acid 380, while cation binding is determined by interactions arising from the amino- and carboxyl-terminal halves of the transporters. Surprisingly, the chimera transported alpha-phenyl derivatives of D-glucose as well as the inhibitors of sugar transport: phlorizin, deoxyphlorizin, and beta-D-glucopyranosylphenyl isothiocyanate are transported with high affinity (K0.5 for phlorizin was 5 microM). Thus, the pocket for organic substrate binding is increased from 10 x 5 x 5 (A) for SGLT1 to 11 x 18 x 5 (A) for the chimera.[1]


  1. Sugar binding to Na+/glucose cotransporters is determined by the carboxyl-terminal half of the protein. Panayotova-Heiermann, M., Loo, D.D., Kong, C.T., Lever, J.E., Wright, E.M. J. Biol. Chem. (1996) [Pubmed]
WikiGenes - Universities