Lecithin:Cholesterol Aeyltransferase Activation and Lipid Binding by Synthetic Fragments of Apolipoprotein C-I

Abstract

Peptide fragments of apolipoprotein C-I (apoLP-C-I) have been synthesized by solid phase methodology. After purification, each peptide showed the correct amino acid analysis and was a single band by polyacrylamide gel electrophoresis. In density gradient ultracentrifugation with vesicles of dimyristoyl phosphatidylcholine, peptide fragments 32-57. 24-57, and 17-57 formed stable complexes while 39-57 did not. With mixed vesicles of dimyristoyl phosphatidylcholine-cholesterol 20 µM of the fragments 32-57, 24-5 7 and 17-57 stimulated lecithin:cholesterol aeyltransferase (LC AT) activity 50,60, and 100%. respectively, of the value found for apolipoprotein C-I, while fragment 39-57 was inactive. The results indicate that residues 17-57 contain the structural requirements for LCAT activation by apoLP-C-I, and that residues 32 57 represent one of the major phospholipid binding regions of apoLP-C-I.

Key Words:

• cholesterol esterification
• circular dichroism
• density gradient ultracentrifugation
• phospholipid protein interaction
• synthetic peptides