Specific binding of the endocytosis tracer horseradish peroxidase to intestinal fatty acid-binding protein (I-FABP) in apical membranes of carp enterocytes.
In a previous study we had demonstrated that a 15-kDa protein present in carp intestinal brush-border membrane vesicles (BBMV) was able to bind the endocytosis tracer horseradish peroxidase (HRP) with high specificity. Here we show that this protein corresponds to a peripheral membrane protein, identified by partial amino acid sequence analysis as the intestinal fatty acid-binding protein (I-FABP), a member of the small cytosolic fatty acid binding protein family (FABPs). The presence of I-FABP and its HRP-binding activity was demonstrated both in the cytosolic and membrane-associated fractions of intestinal mucosa by Western and ligand blot analyses, respectively. Also, both fractions displayed significant capacity to bind [(3)H]palmitic acid, a known ligand for I-FABP. Immunohistochemical analysis showed that I-FABP localizes both in the cytosol and in the brush-border membranes of epithelial cells. Taken together the unusual extra-cellular localization of I-FABP as well as its ability to interact with HRP suggests a novel function for this protein in the intestinal mucosa.
Concha
Margarita I
MI
Instituto de Bioquímica, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile.
Santander
Cristián
C
Villanueva
Julieta
J
Amthauer
Rodolfo
R
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002347:Carps / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity; D004591:Electrophoresis, Polyacrylamide Gel; D004705:Endocytosis; D020895:Enterocytes / Q000166:cytology* / Q000378:metabolism*; D050556:Fatty Acid-Binding Proteins; D006735:Horseradish Peroxidase / Q000378:metabolism*; D007150:Immunohistochemistry; D008871:Microvilli / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D011485:Protein Binding; D011487:Protein Conformation
D002352:Carrier Proteins; D050556:Fatty Acid-Binding Proteins; D009363:Neoplasm Proteins; D006735:Horseradish Peroxidase