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Ligatin: a peripheral membrane protein with covalently bound palmitic acid
The Journal of Biological Chemistry
|January 25, 1987
Summary
Ligatin, a membrane protein, achieves its hydrophobicity not from amino acids but from attached fatty acids. This post-translational modification explains its membrane affinity.
Area of Science:
- Biochemistry
- Molecular Biology
- Membrane Biology
Background:
- Ligatin is a polypeptide with properties similar to Folch-Lee proteolipid.
- Its hydrophobicity suggests membrane interaction, but its amino acid composition lacks enrichment in hydrophobic residues.
Purpose of the Study:
- To investigate the source of ligatin's hydrophobicity and its mechanism of membrane association.
Main Methods:
- Solubility tests in acidified chloroform:methanol.
- Measurement of membrane conductance changes upon ligatin's incorporation into phosphatidylcholine bilayers.
- Gas chromatography mass spectrometry (GC-MS) to analyze fatty acid composition.
Main Results:
- Ligatin exhibits concentration-dependent interpolation into phosphatidylcholine bilayers, altering membrane conductance.
- Amino acid analysis did not reveal enrichment in hydrophobic residues.
- GC-MS identified covalent association with 1.4-1.7 mol of palmitate per 10,000 g of protein.
Conclusions:
- Ligatin's hydrophobic character and membrane affinity are primarily due to post-translational covalent attachment of fatty acids, specifically palmitate.
- This mechanism differs from typical proteolipids that rely on intrinsic amino acid hydrophobicity.