Plasma lipid transport in the preruminant calf, Bos spp: primary structure of bovine apolipoprotein A-I.
The preruminant calf (Bos spp.) is a model of considerable interest with regard to hepatic and intestinal lipoprotein metabolism (Bauchart et al., J. Lipid Res. (1989) 30, 1499-1514 and Laplaud et al., J. Lipid Res. (1990) 31, 1781-1792). As a preliminary step towards future experiments dealing with HDL metabolism in the calf, we have purified apoA-I from this animal and determined its complete amino acid sequence. Thus, approx. 10% of calf apoA-I was shown to contain a propeptide, with the sequence Arg-His-Phe-Trp-Gln-Gln. Enzymatic cleavage of apoA-I resulted in 10 proteolytic peptides. The complete apoA-I sequence was obtained after alignment of peptides on the basis of their homologies with those from rabbit apoA-I. Thus calf apoA-I consists of 241 amino acid residues, and exhibits high sequence homology with all mammalian apoA-I's studied to date. The bovine protein contained 10 hydrophobic amphipathic helical regions, occurring between residues 43-64, 65-86, 87-97, 98-119, 120-141, 142-163, 164-184, 185-206, 207-217 and 218-241. A computer-constructed phylogenetic tree showed that bovine apoA-I was more closely related to its dog counterpart, including the presence of a single methionine, than to the corresponding macaque and human proteins. Comparative predictions of the respective antigenic structures of human and bovine apoA-I's using the Hopp-Woods algorithm indicated similar positions for all 13 detectable antigenic sites, among which 7 were of identical, or closely related, amino acid composition. This finding was confirmed by demonstration of partial immunological identity between the two proteins upon immunodiffusion analysis, a result obtained using a monospecific rabbit antiserum against bovine apoA-I. Finally, comparison of sequence homology between bovine apoA-I and the lecithin:cholesterol acyl transferase (LCAT) activating region of human apoC-I suggests that several LCAT activating domains may be present in calf apoA-I.
Sparrow
D A
DA
Department of Medicine, Baylor College of Medicine, Houston, TX 77030.
Lee
B R
BR
Laplaud
P M
PM
Auboiron
S
S
Bauchart
D
D
Chapman
M J
MJ
Gotto
A M
AM
Yang
C Y
CY
Sparrow
J T
JT
D000595:Amino Acid Sequence; D000818:Animals; D016632:Apolipoprotein A-I / Q000737:chemistry* / Q000276:immunology / Q000302:isolation & purification; D001692:Biological Transport; D002417:Cattle; D003429:Cross Reactions; D004285:Dogs; D006801:Humans; D007106:Immune Sera; D008075:Lipoproteins, HDL / Q000737:chemistry / Q000276:immunology; D008297:Male; D008969:Molecular Sequence Data; D011817:Rabbits; D051381:Rats; D013045:Species Specificity; D013329:Structure-Activity Relationship
D016632:Apolipoprotein A-I; D007106:Immune Sera; D008075:Lipoproteins, HDL