Effects of Cys mutation on taurocholic acid transport by mouse ileal and hepatic sodium-dependent bile acid transporters.

All cysteines of mouse ileal and hepatic sodium-dependent bile acid transporters (Isbt and Ntcp, respectively) were individually replaced by alanine. Replacement of Cys106 in Isbt and Cys96 in Ntcp, which are located closely in alignment, decreased taurocholate uptake. Although Cys51 in Isbt is conserved in Ntcp, the replacement spoiled Isbt only. Both similarity and difference in the arrangement of functional sites are suggested.