Identification and functional characterization of the bile acid transport proteins in non-mammalian ileum and mammalian liver.
It has been proposed that intracellular carrier proteins mediate active transport of the bile acids within hepatocytes and ileocytes, during the enterohepatic circulation. In mammalian species only ileal bile acid binding proteins have been so far identified, while liver cytosolic carriers have never been found. On the contrary, in non-mammalian vertebrates, only liver, and not ileal, bile acid binding proteins were reported. The aim of the present work is to find the missing cytosolic transport proteins. A bioinformatic search allowed us to identify a non-mammalian putative bile acid binding protein in the chicken ileum (cI-BABP), which we recombinantly expressed and purified. The protein exhibits the capability, tested by in vitro NMR experiments, of binding bile acids. Furthermore, strong NMR evidence reported that the human liver fatty acid binding protein (hL-FABP) can also bind bile acids. Taken together, these data strongly suggest that both cI-BABP and hL-FABP have a bile acid binding function in the two organisms, and support a previous hypothesis on the role of hL-FABP in regulating bile acid metabolism and determining bile acid pool size.
Guariento
Mara
M
Dipartimento Scientifico e Tecnologico, Strada Le Grazie 15, 37134 Verona, Italy.
Raimondo
Domenico
D
Assfalg
Michael
M
Zanzoni
Serena
S
Pesente
Patrizia
P
Ragona
Laura
L
Tramontano
Anna
A
Molinari
Henriette
H
D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry*; D002645:Chickens; D006801:Humans; D007082:Ileum / Q000737:chemistry*; D008099:Liver / Q000737:chemistry*; D008562:Membrane Glycoproteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
D002352:Carrier Proteins; D008562:Membrane Glycoproteins; C037643:bile acid binding proteins