Expression, Purification, and Biochemical Characterization of Human Afamin

Area of Science:

• Biochemistry
• Molecular Biology
• Glycobiology

Background:

• Afamin is an 87 kDa glycoprotein with five N-glycosylation sites.
• Glycosylation leads to heterogeneity, complicating structural determination of afamin.
• Antibody fragments can stabilize proteins for crystallization.

Purpose of the Study:

• To produce and characterize recombinant human afamin (rhAFM) with varying glycosylation patterns.
• To investigate the role of glycosylation in afamin expression, secretion, and structural stability.
• To facilitate afamin structure determination through complex formation with antibody fragments.

Main Methods:

• Recombinant expression of wild-type, hypoglycosylated, and nonglycosylated rhAFM in CHO, CHO-Lec1, and HEK293T cells.
• Purification using immobilized metal ion affinity and size exclusion chromatography.
• Glycan analysis and complex formation with anti-afamin Fab fragment (N14).

Main Results:

• Successfully expressed and purified various glycosylated forms of rhAFM.
• Demonstrated that glycosylation is not required for afamin expression and secretion.
• Characterized glycosylation heterogeneity, enabling comparisons between different afamin forms.
• Formed a stoichiometric complex between rhAFM and the N14 Fab fragment.

Conclusions:

• Glycosylation is not essential for the expression and secretion of human afamin.
• Production of hypo- and nonglycosylated afamin facilitates structural studies.
• Complex formation with antibody fragments may aid in afamin crystallization and structure determination.