Characterization, cDNA cloning, and functional expression of mouse ileal sodium-dependent bile acid transporter.

T Saeki, K Matoba, H Furukawa, K Kirifuji, R Kanamoto, K Iwami

Laboratory of Molecular Nutrition, Department of Biological Resource Chemistry, Kyoto Prefectural University, Shimogamo, Sakyo-ku, Kyoto, 606-8522, Japan. tsaeki@dns.kpu.ac.jp

Journal of biochemistry 1999 Apr

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Mouse ileal sodium dependent bile acid transporter (ISBT) was characterized using isolated enterocytes. Only enterocytes from the most distal portion showed Na+-dependent [3H]taurocholate uptake. Northern blot analysis using a probe against mouse ISBT revealed the expression of mouse ISBT mRNA to be restricted to the distal ileum. The Km and Vmax for Na+-dependent [3H]taurocholate transport into isolated ileocytes were calculated as 27 microM and 360 pmol/mg protein/min, respectively. Uptake of [3H]taurocholate was inhibited by N-ethylmaleimide. We have cloned ISBT cDNA from mouse ileum. The cDNA included the entire open reading frame coding 348 amino acid protein with seven hydrophobic segments and two N-glycosylation sites. COS-7 cells transfected with the expression vector containing this cDNA expressed Na+-dependent [3H]taurocholate uptake activity with a Km of 34 microM.

Citation

T Saeki, K Matoba, H Furukawa, K Kirifuji, R Kanamoto, K Iwami. Characterization, cDNA cloning, and functional expression of mouse ileal sodium-dependent bile acid transporter. Journal of biochemistry. 1999 Apr;125(4):846-51