Identification of a mutation in the ileal sodium-dependent bile acid transporter gene that abolishes transport activity.
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Wong MH, Oelkers P, Dawson PA
Identification of a mutation in the ileal sodium-dependent bile acid transporter gene that abolishes transport activity.
J Biol Chem. 1995 Nov 10;270(45):27228-34.
- PubMed ID
- 7592981 [ View in PubMed]
- Abstract
The ileal Na+/bile acid cotransporter plays a critical role in the reabsorption of bile acids from the small intestine. In the course of cloning and characterizing the human ileal Na+/bile acid cotransporter cDNA, a dysfunctional isoform was identified in a patient diagnosed with Crohn's disease. Expression studies using hamster-human ileal Na+/bile acid cotransporter cDNA chimeras narrowed the location of the defect to the carboxyl-terminal 94 amino acids. Comparison of the sequence of the dysfunctional isoform to that of a wild-type human ileal Na+/bile acid cotransporter genomic clone revealed a single C to T transition resulting in a proline to serine substitution at amino acid position 290. The inheritance of this mutation in the proband's family was confirmed by single-stranded conformation polymorphism analysis and DNA sequencing. In transfected COS-1 cells, the single amino acid change abolished taurocholate transport activity but did not alter the transporter's synthesis or subcellular distribution. This dysfunctional mutation represents the first known molecular defect in a human sodium-dependent bile acid transporter.