Cardiac fatty acid-binding proteins. Isolation and characterization of the mitochondrial fatty acid-binding protein and its structural relationship with the cytosolic isoforms.
In the course of our studies on the structural diversity of the isoforms of cardiac fatty acid-binding proteins (cFABPs), a cardiac-type FABP from the matrix of bovine heart mitochondria was purified to homogeneity and obtained as a single 15-kDa protein with an isoelectric point of 4.9. The primary structures of this protein and of the two isoforms isolated from the cytosol (pI4.9-cFABP and pI 5.1-cFABP) were investigated by means of plasma desorption mass spectrometry and sequencing of peptides. All three proteins are amino-terminally blocked with an acetyl group and shown to be colinear with the sequence deduced from a cDNA clone for bovine heart fatty acid-binding protein (Billich, S., Wissel, T., Kratzin, H., Hahn, U., Hagenhoff, B., Lezius, A. G., and Spener, F. (1988) Eur. J. Biochem. 175, 549-556) except for the residue at position 98. This residue is demonstrated to be the molecular origin of bovine cFABP isoforms since pI 5.1-cFABP contains Asn98 in accordance with the sequence derived from the cDNA, whereas in pI 4.9-cFABP, this position is occupied by Asp98. Moreover, mitochondrial FABP is identical to pI 4.9-cFABP. Molecular masses of pI 4.9-cFABP (14,679 +/- 10 Da) and pI 5.1-cFABP (14,678 +/- 20 Da) determined by plasma desorption mass spectrometry coincide with that calculated from the cDNA (14,673 Da). Hence, residues linked to these proteins by posttranslational modification are not present, and the Asn-Asp exchange is the sole origin of heterogeneity of mitochondrial and cytosolic fatty acid-binding proteins from bovine heart.
Unterberg
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C
Department of Biochemistry, University of Münster, Federal Republic of Germany.
Börchers
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Højrup
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Roepstorff
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Knudsen
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Spener
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D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002417:Cattle; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D003600:Cytosol / Q000378:metabolism; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism; D013058:Mass Spectrometry; D008929:Mitochondria, Heart / Q000378:metabolism*; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism*; D009363:Neoplasm Proteins; D010446:Peptide Fragments / Q000302:isolation & purification; D010449:Peptide Mapping; D012689:Sequence Homology, Nucleic Acid
D002352:Carrier Proteins; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D009363:Neoplasm Proteins; D010446:Peptide Fragments