Bovine epidermal fatty acid-binding protein: determination of ligand specificity and cellular localization in retina and testis.
The fatty acid-binding protein (FABP) family consists of small, cytosolic proteins believed to be involved in the uptake, transport, and solubilization of their hydrophobic ligands. Members of this family have highly conserved sequences and tertiary structures. Using an antibody against testis lipid-binding protein, a member of the FABP family, a protein was identified from bovine retina and testis that coeluted with exogenously added docosahexaenoic acid during purification. Amino acid sequencing and subsequent isolation of its cDNA revealed it to be nearly identical to a bovine protein expressed in the differentiating lens and to be the likely bovine homologue of the human epidermal fatty acid-binding protein (E-FABP). From quantitative Western blot analysis, it was estimated that bovine E-FABP comprised 0.9%, 0.1%, and 2.4% of retina, testis, and lens cytosolic proteins, respectively. Binding studies using the fluorescent probe ADIFAB indicated that this protein bound fatty acids of differing levels of saturation with relatively high affinities. Kd values ranged from 27 to 97 nM. In addition, the protein was immunolocalized to the Müller cells in the retina as well as to Sertoli cells in the testis. The location of bovine E-FABP in cells known to be supportive to other cell types in their tissues and the ability of E-FABP to bind a variety of fatty acids with similar affinities indicate that it may be involved in the uptake and transport of fatty acids essential for the nourishment of the surrounding cell types.
Kingma
P B
PB
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
Bok
D
D
Ong
D E
DE
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D018076:DNA, Complementary / Q000235:genetics; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007700:Kinetics; D007908:Lens, Crystalline / Q000378:metabolism; D008024:Ligands; D008297:Male; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D018996:Myelin P2 Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins; D012160:Retina / Q000378:metabolism* / Q000648:ultrastructure; D012708:Sertoli Cells / Q000378:metabolism; D012867:Skin / Q000378:metabolism; D013737:Testis / Q000378:metabolism*; D025521:Tumor Suppressor Proteins
D002352:Carrier Proteins; D018076:DNA, Complementary; C493412:FABP5 protein, human; C107608:FABP7 protein, human; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D008024:Ligands; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D025521:Tumor Suppressor Proteins