J. Biol. Chem., Vol. 261, Issue 18, 8218-8223, Jun, 1986
Rat heart fatty acid-binding protein is highly homologous to the murine adipocyte 422 protein and the P2 protein of peripheral nerve myelin
JC Sacchettini, B Said, H Schulz and JI Gordon
The rat heart contains an abundant cytosolic protein which binds long chain
fatty acids. We have determined its primary structure by Edman degradation
of peptides generated from chymotryptic, tryptic, and elastase digestions.
This polypeptide (Mr = 14,992) contains 134 amino acids and has a blocked
(acetylated) NH2 terminus. The sequence of rat heart fatty acid-binding
protein (FABP) is remarkably similar to the murine adipocyte 422 protein
and the P2 protein of peripheral nerve myelin. Computer-assisted alignment
of heart FABP and 422 revealed that 82 of 132 comparable residues are
identical (62%). There are 77 identities out of 131 possible matches
between this protein and the human myelin P2 protein (59%). Similar
comparisons demonstrate that heart FABP has significant homology to several
other proteins which bind hydrophobic ligands. The rank of order of
similarity to heart FABP is: 422 greater than myelin P2 greater than
cellular retinoic acid- binding protein greater than cellular
retinol-binding protein II greater than cellular retinol-binding protein
greater than intestinal FABP greater than liver FABP. These eight sequences
form a family of paralogous homologues. Heart FABP has a region of internal
homology involving tandemly arrayed oligopeptides spanning residues 71-100
and 101-131. This feature is not found in the 422 and P2 sequences. The
endogenous ligands bound by the 422, P2, and heart FABP sequences have not
been defined. Interpretation of the biological significance of their
structural similarities and differences will require information about
their ligand specificities and affinities.