The human and rodent intestinal fatty acid binding protein genes: A comparative analysis of their structure, expression, and linkage relationships

D. A. Sweetser, E. H. Birkenmeier, I. J. Klisak, S. Zollman, R. S. Sparkes, T. Mohandas, A. J. Lusis, J. I. Gordon

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Intestinal fatty acid binding protein (I-FABP) is believed to participate in the uptake, intracellular metabolism, and/or transport of long chain fatty acids within enterocytes. The 15.1-kDa rodent protein is a member of a family of low M(r) cytoplasmic proteins that have evolved to bind different ligands. We have now determined the nucleotide sequence of the gene encoding human I-FABP and defined the primary structure of its protein product. The human I-FABP gene spans 3382 nucleotides and contains 4 exons (103 or 128, 173, 108, and 312 base pairs) interrupted by 3 introns (1194, 1023, and 444 base pairs). The 132-residue rat and human I-FABPs have 82% amino acid sequence identity. Blot hybridization studies of RNAs prepared from a variety of adult rhesus monkey tissues as well as human intestine and liver indicate that I-FABP mRNA is confined to the intestine. I-FABP mRNA was not detectable in a number of cultured human enterocyte-like cell lines, suggesting it may be a sensitive marker for differentiated, villus-associated, small intestinal lining cells. Given the similar patterns of tissue-specific expression exhibited by the rat and human genes, we compared their 5' nontranscribed regions. Optimal alignments of the two sequences disclosed 64% identity among the 260 nucleotides immediately 5' to the start site of transcription. Matrix plots revealed a 14-nucleotide long repeated sequence (5'-TGAACTTTGAACTT-3') in the 5' nontranscribed region of both genes as well as in a comparable region of another family member that is expressed in enterocytes, cellular retinol binding protein II. The linkage relationships between I-FABP and the homologous liver FABP (L-FABP) gene were defined in mice and humans. The mouse genes were mapped using restriction fragment length polymorphisms and recombinant inbred strains. The I-FABP gene is located on mouse chromosome 3 between the amylase 1,2 (Amy 1,2) and alcohol dehydrogenase 3 (Adh-3) loci while the L-FABP gene is on mouse chromosome 6 within 3 centimorgans of the lymphocyte antigen-2 (Ly-2) locus. Mouse L-FABP may be identical to the major liver protein-1 (Lvp-1) which is encoded by a gene situated within a centimorgan of Ly-2. Human gene mapping studies were carried out using a panel of mouse-human somatic cell hybrid clones as well as in situ hybridization to metaphase chromosomes. The I-FABP gene is located in the q28-q31 region of human chromosome 4 while the L-FABP gene resides in the p12-q11 region of human chromosome 2. These findings extend the regions of syntenic homology that exist between these human and mouse chromosomes.

Original languageEnglish
Pages (from-to)16060-16071
Number of pages12
JournalJournal of Biological Chemistry
Issue number33
StatePublished - 1987


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