Substrate specificity of a chimera made from Xenopus SGLT1-like protein and rabbit SGLT1 |
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Authors: | Katsumi Nagata Yoshio Hata |
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Affiliation: | Department of Biomedical Science, Institute of Regenerative Medicine and Biofunction, Tottori University Graduate School of Medical Science, Nishimachi 86, Yonago 683-8503, Japan |
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Abstract: | ![]() To characterize the sugar translocation pathway of Na+/glucose cotransporter type 1 (SGLT1), a chimera was made by substituting the extracellular loop between transmembrane domain (TM) 12 and TM13 of Xenopus SGLT1-like protein (xSGLT1L) with the homologous region of rabbit SGLT1. The chimera was expressed in Xenopus oocytes and its transport activity was measured by the two-microelectrode voltage-clamp method. The substrate specificity of the chimera was different from those of xSGLT1L and SGLT1. In addition the chimera's apparent Michaelis-Menten constant (Km) for myo-inositol, 0.06 mM, was about one fourth of that of xSGLT1L, 0.25 mM, while the chimera's apparent Km for d-glucose, 0.8 mM, was about one eighth of that of xSGLT1L, 6.3 mM. Our results suggest that the extracellular loop between TM12 and TM13 participates in the sugar transport of SGLT1. |
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Keywords: | Xenopus SGLT1-like protein SGLT SMIT Chimera |
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