Purification and characterization of two mannan-binding lectins from mouse serum

Area of Science:

• Immunology
• Biochemistry
• Molecular Biology

Background:

• Mannan-binding lectin (MBL) is a key serum protein initiating the complement system by binding microbial glycoconjugates.
• Two mouse MBL forms, mMBL-A and mMBL-C, have been identified, with mMBL-A previously characterized at the protein level.
• mMBL-C is recognized as the liver-specific MBL form.

Purpose of the Study:

• To purify and characterize both mMBL-A and mMBL-C from mouse serum.
• To compare the biochemical and functional properties of mMBL-A and mMBL-C.
• To determine serum concentrations of mMBL-A in different mouse populations.

Main Methods:

• Ion-exchange and carbohydrate-affinity chromatography for protein separation.
• Immunochemical techniques and N-terminal amino-acid sequencing for identification.
• SDS-PAGE, acid/urea-PAGE, and complement component C4 activation assays for characterization.

Main Results:

• mMBL-A and mMBL-C were successfully purified and separated.
• Both mMBL forms activated complement component C4.
• mMBL-A exhibited higher affinity for specific glucose derivatives compared to mMBL-C.
• Serum concentrations of mMBL-A ranged from 5 to 80 microg/ml, with wild mice having higher levels than laboratory strains.

Conclusions:

• Both mMBL-A and mMBL-C are functional forms of MBL capable of activating the complement system.
• Distinct biochemical properties, including carbohydrate-binding affinity, differentiate mMBL-A and mMBL-C.
• Significant variations in mMBL-A serum levels exist between wild and laboratory mice, suggesting potential ecological or genetic influences.