Document Detail

Apolipoprotein C-III0 lacks carbohydrate residues: use of mass spectrometry to study apolipoprotein structure.
MedLine Citation:
PMID:  2614277     Owner:  NLM     Status:  MEDLINE    
Apolipoprotein C-III (apo C-III) is a 79 amino acid glycoprotein. The sugar moiety of apoC-III is attached to amino acid residue 74 and is thought to consist of 1 mole of galactose, 1 mole of N-acetyl-galactosamine, and either 0, 1, or 2 moles of sialic acid. This results in three isoproteins called C-III0, C-III1, and C-III2 designated by the number of sialic acid residues. It has been assumed, although not experimentally tested, that apoC-III0 lacks sialic acid residues but possesses the D-galactosyl-(1-3)-N-acetyl-D-galactosamine sugar backbone. To verify the structure of the three apoC-III isoproteins, we applied the method of 252Cf plasma desorption mass spectrometry to measure the exact molecular weight (Mr) of each of the isoproteins. Our data confirmed the proposed structure of apoC-III1 and apoC-III2. However, the difference in mass between apoC-III1 (9420.6, 9420.0, 9422.2 daltons) and apoC-III0 (8763.9, 8764.9, 8765.5 daltons, respectively, in three subjects) suggests that the latter is missing not just sialic acid but the entire sugar moiety. This finding may have important implications for the metabolism of apoC-III. The accuracy and reproducibility of Mr measurements described in this paper suggest that this technique holds promise for the detection of apolipoprotein amino acid substitutions or modifications undetected by conventional techniques such as isoelectric focusing.
Y Ito; J L Breslow; B T Chait
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of lipid research     Volume:  30     ISSN:  0022-2275     ISO Abbreviation:  J. Lipid Res.     Publication Date:  1989 Nov 
Date Detail:
Created Date:  1990-03-01     Completed Date:  1990-03-01     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0376606     Medline TA:  J Lipid Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1781-7     Citation Subset:  IM    
Laboratory of Biochemical Genetics and Metabolism, Rockefeller University, New York, NY 10021.
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MeSH Terms
Apolipoprotein C-III
Apolipoproteins C / blood*
Carbohydrates / analysis*
Chromatography, Ion Exchange
Hypertriglyceridemia / blood
Isoelectric Focusing
Lipoproteins, VLDL / blood
Mass Spectrometry
Molecular Structure
Molecular Weight
Grant Support
Reg. No./Substance:
0/Apolipoprotein C-III; 0/Apolipoproteins C; 0/Carbohydrates; 0/Lipoproteins, VLDL

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