Plasma membrane fatty-acid-binding protein in human placenta: identification and characterization

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Biology

Background:

• Fatty-acid-binding proteins (FABPs) are involved in lipid metabolism and transport.
• A plasma membrane-associated FABP (FABPpm) has been identified in various tissues, but its specific role in human placenta is less understood.

Purpose of the Study:

• To identify and characterize a fatty-acid-binding protein (FABPpm) in human placental plasma membranes.
• To investigate the binding characteristics and properties of this placental FABPpm.

Main Methods:

• Isolation and purification of FABPpm from human placental membranes.
• Fatty acid binding assays using radiolabeled oleate and linoleate.
• Competition assays with other molecules and enzymatic treatments (trypsin).
• Protein characterization including pI and amino acid composition analysis.
• Confirmation of binding activity using autoradioblotting and antibody inhibition.

Main Results:

• A 40 kDa FABPpm was identified in human placental membranes with time and temperature-dependent binding of oleate and linoleate.
• Binding was specific for fatty acids, as indicated by lack of competition with sulphobromophthalein and alpha-tocopherol.
• Trypsin treatment reduced binding, confirming the protein nature of the binding sites.
• Purified placental FABPpm retained fatty acid binding activity, confirmed by autoradioblotting.
• Antiserum against placental FABPpm significantly reduced fatty acid binding.
• Placental FABPpm differs in pI and amino acid composition from hepatic FABPpm.

Conclusions:

• A distinct plasma membrane fatty-acid-binding protein (FABPpm) exists in human placenta.
• This protein specifically binds fatty acids and is involved in their transport across the placental membrane.
• Placental FABPpm is biochemically distinct from the previously characterized hepatic FABPpm.