Isolation and identification of a mouse brain protein recognized by antisera to heart fatty acid-binding protein.
Although a novel brain-specific fatty acid-binding protein (B-FABP) was recently cloned, the identity of a second fatty acid-binding protein detected with antibodies to the heart (H-FABP) has not been clearly resolved. The present investigation, using matrix-assisted laser desorption mass spectrometry, showed that this protein was a form of H-FABP whose N-terminal amino acid was neither methionine nor was it acetylated. Furthermore, isoelectric focusing revealed two major isoforms, a major band pl 7.4 and a minor band pl 6.4, in a distribution pattern opposite to that observed for H-FABP in the heart. Tryptic peptide mass maps of the in-gel digested SDS polyacrylamide gel electrophoresis protein bands showed that the two isoforms differed only in a single peptide corresponding to residues 97-106 of the heart H-FABP sequence. This peptide had an [M + H]+ ion of either 1205.62 (pl 7.4) or 1206.53 (pl 6.4), consistent with a single amino acid substitution, Asp98 or Asn98. Whereas it is well established that both H-FABP and B-FABP interact with polyunsaturated fatty acids, we showed that they also significantly alter plasma membrane cholesterol dynamics in a manner opposite to that of another brain lipid-binding protein, sterol carrier protein-2. In summary, the data demonstrated for the first time that the H-FABP from brain, while nearly identical to H-FABP from heart, differed significantly in isoform distribution and in amino terminal structure from heart H-FABP. This suggests that the brain and heart H-FABP may not necessarily function identically in these tissues.
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Department of Physiology and Pharmacology, Texas A&M University, TVMC, College Station 77843-4466, USA.
Annan
R S
RS
Carr
S A
SA
Frolov
A
A
Wood
W G
WG
Spener
F
F
Schroeder
F
F
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification*; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D007106:Immune Sera; D007525:Isoelectric Focusing; D051379:Mice; D008969:Molecular Sequence Data; D018996:Myelin P2 Protein / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010449:Peptide Mapping; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D002352:Carrier Proteins; C082667:Fabp5 protein, mouse; C086936:Fabp7 protein, mouse; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D007106:Immune Sera; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins