Characterization of the oligomer structure of recombinant human mannan-binding lectin.
Mannan-binding lectin (MBL) belongs to a family of proteins called the collectins, which show large differences in their ultrastructures. These differences are believed to be determined by different N-terminal disulfide-bonding patterns. So far only the bonding pattern of two of the simple forms (recombinant rat MBL-C and bovine CL-43) have been determined. Recombinant MBL expressed in human cells was purified, and the structure of the N-terminal region was determined. Preliminary results on human plasma-derived MBL revealed high similarity to the recombinant protein. Here we report the structure of the N-terminal part of recombinant human MBL and present a model to explain the oligomerization pattern. Using a strategy of consecutive enzymatic digestions and matrix-assisted laser desorption ionization mass spectrometry, we succeeded in identifying a number of disulfide-linked peptides from the N-terminal cysteine-rich region. Based on these building blocks, we propose a model that can explain the various oligomeric forms found in purified MBL preparations. Furthermore, the model was challenged by the production of cysteine to serine mutants of the three N-terminally situated cysteines. The oligomerization patterns of these mutants support the proposed model. The model indicates that the polypeptide dimer is the basic unit in the oligomerization.
Jensen
Pia H
PH
Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark.
Weilguny
Dietmar
D
Matthiesen
Finn
F
McGuire
Kirsten A
KA
Shi
Lei
L
Højrup
Peter
P
D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D006801:Humans; D037601:Mannose-Binding Lectin / Q000737:chemistry*; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry
D004220:Disulfides; D037601:Mannose-Binding Lectin; D021122:Protein Subunits; D011994:Recombinant Proteins