P. Storgaard et al., ISOLATION AND CHARACTERIZATION OF PORCINE MANNAN-BINDING PROTEINS OF DIFFERENT SIZE AND ULTRASTRUCTURE, Scandinavian journal of immunology, 43(3), 1996, pp. 289-296
The authors report on the purification and characterization of mannan-
binding proteins (MBP) isolated from porcine serum. The MBPs were puri
fied by use of PEG precipitation, affinity chromatography on mannan-Se
pharose, protein A- and anti-porcine IgM-Sepharose followed by gel fil
tration. The MBP proteins were collagenase sensitive and showed gamma(
1)-gamma(2)-electrophoretic mobility. The MBP designated pMBP-28 had a
molecular mass of 28 kDa when analysed on SDS-PAGE under reducing con
ditions and eluted corresponding to a molecular mass of approximately
700 kDa on gel filtration chromatography. Electron micrographs of pMBP
-28 revealed an oligomeric protein similar to rodent MBP-A and human M
BP but with a predominance of penta- and hexameric molecules. Another
protein designated pMBP-27 was composed of peptides of 27 kDa and had
an M(r) of 300-350 kDa on gel filtration chromatography. Electron micr
oscopy of pMBP-27 showed dimer and trimer molecules; the trimers witho
ut distinct stalk regions. The N-terminal 26 (pMBP-27) and 24 (MBP-28)
amino acid residues showed 54% and 58% identity with human MBP. pMBP-
28 showed a higher degree of sequence similarity to rat and mouse MBP-
A (60% identity) than to mouse and rat MBP-C (41-45% identity). Both p
MBPs exhibited Ca2+-dependent binding to D-mannose immobilized on agar
ose but no significant binding to N-acetyl-D-glucosamine- or fucose-ag
arose. The results further suggested the presence of a third pMBP whic
h copurified with pMBP-27 but this protein was not sequenced.