Conformational studies of the mimotope peptide of apolipoprotein A-I and B-100 by NMR spectroscopy

Abstract

Apolipoproteins are protein components of lipoproteins exhibiting major roles in the transport of plasma lipids and used clinically for the of coronary artery disease. A number of mimetic peptides of apolipoproteins were screened from the phage-displayed random peptide library by using a biopanning method. The mimetic peptides were recognized by the monoclonal antibody against apo A-I were CPFARLPVEHHDVVGL(pA1) and FVLVRDTFPSSVCCP(pA2) and the mimetic peptide were recognized by apo B-100 specific monoclonal antibody was CRNVPPIFNDVYWIAF(pB1). Theses amino acid sequences of peptides are not in original antigens apo A-I, apo B-100. Compared with primary arrangement of amino acid using of BLAST search, pA1, pA2 were confirmed 40％, 45％ homology with apo A-I and pB1 were confirmed 40％ homology with apo B-100. In this study, 1H-NMR and 2D NMR(COSY, TOCSY, NOESY) experiments were accomplished and signal assignments of mimotope peptides were made. Distance of numerous proton paris were obtained based on the NOE cross peak intensities of NOESY spectrum. On the basis of these distance data, distance geometry(DG) and molecular dynamic(MD) were carried out to determine the tertiary structure of mimotope pA1, pA2 and pB1. DG structures of three mimotope pA1, pA2, pB1 were low penalty value 0.3～0.6Å2, and the total RMSD obtained upon superposition of all atoms were in the range 0.5～1.5Å. Mimotope pA1 has β-turn conformation from residue Pro7 to His11, and pA2 has β-turn conformation from residue Val2 to Phe8. pB1 has a similar 310-helix structure from Ile7 to Trp13.