Mass spectral analysis of domestic and wild equine apoA-I and A-II: detection of unique dimeric forms of apoA-II.
In pigs, humans, chimpanzees and probably other great apes, a cysteine at residue 6 enables apolipoprotein A-II to form a homodimer. However, the apoA-IIs of other primates, lacking a cysteine residue, are monomeric. We have already reported that horse apoA-IIs form homodimers due also to a cysteine at residue 6. In this study, we wanted to determine whether other equine apoA-IIs might be monomeric. The high density lipoproteins were ultracentrifugally isolated from the plasmas of a horse (Equus caballus), a donkey (Equus asinus) and five wild equines: two types of zebras (Equus zebra hartmannae and Equus zebra quagga boehmi), a Przewalski's horse (Equus przewalskii), a Somali ass (Equus africanus somalicus) and a kiang (Equus kiang holdereri). Using liquid chromatography with electrospray-ionization mass spectrometry, we were able to obtain accurate values for the molecular masses of apoA-I and apoA-II. Homodimeric apoA-IIs were observed in each of the animals studied. The donkey had unique dimers, consisting of the proapolipoprotein A-II linked by a disulfide bond either to a mature apoA-II monomer or another proapoA-II. In addition, our data indicate that small amounts of apoA-I and apoA-II apparently are acylated.
Puppione
Donald L
DL
The Molecular Biology Institute and The Department of Chemistry and Biochemistry, University of California at Los Angeles, 90095, USA. puppione@chem.ucla.edu
Whitelegge
Julian P
JP
Yam
Lang M
LM
Bassilian
Sara
S
Schumaker
Verne N
VN
MacDonald
Melinda H
MH
D000818:Animals; D000829:Animals, Domestic; D016632:Apolipoprotein A-I / Q000032:analysis* / Q000097:blood / Q000737:chemistry*; D016633:Apolipoprotein A-II / Q000032:analysis* / Q000097:blood / Q000737:chemistry*; D002850:Chromatography, Gel; D019281:Dimerization; D018397:Equidae / Q000378:metabolism*; D005260:Female; D006736:Horses; D008075:Lipoproteins, HDL / Q000097:blood / Q000737:chemistry; D013058:Mass Spectrometry; D008970:Molecular Weight; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D008075:Lipoproteins, HDL