Details

Autor(en) / Beteiligte

• Xu, Ning
• Dahlbäck, Björn

Titel

A Novel Human Apolipoprotein (apoM)

Ist Teil von

• The Journal of biological chemistry, 1999-10, Vol.274 (44), p.31286-31290

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

1999

Link zum Volltext

Quelle

Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals

Beschreibungen/Notizen

• A novel human apolipoprotein designated apolipoprotein M (apoM) is described. The unique N-terminal amino acid sequence of apoM was found in an approximately 26-kDa protein present in a protein extract of triglyceride-rich lipoproteins (TGRLP). The isolated apoM cDNA (734 base pairs) encoded a 188-amino acid residue-long protein, distantly related to the lipocalin family. The mRNA of apoM was detected in the liver and kidney. Western blotting demonstrated apoM to be present in high density lipoprotein (HDL) and to a lesser extent in TGRLP and low density lipoproteins (LDL). The first 20 amino acid residues of apoM constituted a hydrophobic segment with characteristic features of a signal peptide. This was retained in the mature protein because of the lack of a signal peptidase cleavage site. In vitro translation in the presence of microsomes demonstrated translocation of apoM over the membrane and glycosylation but no signal peptide cleavage. The in vitro translated product remained associated with the microsomes after treatment with carbonate at pH 11, demonstrating that apoM is an integral protein. This finding suggests that apoM is linked to the single phospholipid layer of lipoproteins with a hydrophobic signal anchor. In conclusion, a novel human apolipoprotein, the function of which remains to be determined, is described.