Structure and conformational analysis of lipid-associating peptides of apolipoprotein B-100 produced by trypsinolysis.
Apolipoprotein B-100 (apo B-100) contains putative lipid-associating regions that are, in part, responsible for its overall structure in human plasma low-density lipoproteins. Some of these regions have been identified by reassembly of the total tryptic peptides of apo B-100 with bovine brain sphingomyelin, 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) and dimyristoylphosphatidylcholine (DPMC). Although more than 500 tryptic peptides are predicted from the known number of arginines and lysines in apo B-100, significant amounts of only 13 peptides spontaneously associate with all three phospholipids. These peptides share some structural characteristics, as predicted by several algorithms, that distinguish them from the water-soluble apolipoproteins. Most apolipoproteins associate with lipids via amphipathic helices and are highly helical in native and reassembled lipoproteins. Analysis of all apo B-100 lipophilic peptides by circular dichroism and by use of a predictive algorithm reveals no evidence of amphipathic helices. Although the predictive algorithm suggested that the lipophilic peptides of apo B-100 contain the sequence determinants for beta-sheet, no spectroscopic evidence for this structure was found. We conclude that the lipophilic regions of apo B-100 liberated by trypsinolysis are highly hydrophobic, although their secondary structures do not fit any simple model.
Yang
C Y
CY
Division of Atherosclerosis, Baylor College of Medicine, Houston, Texas.
Kim
T W
TW
Pao
Q
Q
Chan
L
L
Knapp
R D
RD
Gotto
A M
AM
Pownall
H J
HJ
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001055:Apolipoproteins B / Q000032:analysis / Q000378:metabolism*; D001665:Binding Sites; D002942:Circular Dichroism; D004134:Dimyristoylphosphatidylcholine / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000302:isolation & purification / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D011487:Protein Conformation; D013109:Sphingomyelins / Q000378:metabolism; D014357:Trypsin
D000596:Amino Acids; D001055:Apolipoproteins B; D010446:Peptide Fragments; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D014357:Trypsin; C028694:1-palmitoyl-2-oleoylphosphatidylcholine; D004134:Dimyristoylphosphatidylcholine