A small bispecific protein selected for orthogonal affinity purification.

Area of Science:

• Protein Engineering
• Biotechnology
• Affinity Ligands

Background:

• The albumin-binding domain (ABD*) is a small, 46-amino acid scaffold with inherent affinity for human serum albumin (HSA).
• Engineering novel protein domains with multiple specificities is crucial for advanced biotechnological applications, including purification and diagnostics.

Purpose of the Study:

• To create a novel protein domain with dual affinity for human serum albumin (HSA) and protein A (or Z2 domain).
• To develop and validate an orthogonal affinity purification strategy utilizing the engineered dual-affinity domain.

Main Methods:

• Construction of a randomized library based on the albumin-binding domain (ABD*) scaffold.
• Selection of dual-affinity binders using phage display technology.
• Characterization of the selected domain (ABDz1) for secondary structure and ligand binding affinities.
• Development and testing of orthogonal affinity purification strategies using HSA and protein A matrices.

Main Results:

• A novel bifunctional protein domain, ABDz1, was successfully selected, exhibiting affinity for both HSA and protein A.
• The engineered ABDz1 variant demonstrated improved affinity for HSA compared to the parental ABD* molecule.
• Homogeneous purification of ABDz1 was achieved using both HSA and protein A affinity matrices.
• Orthogonal affinity purification using both ligands enabled efficient purification of gene-fusion proteins.

Conclusions:

• A novel, small, dual-affinity protein domain (ABDz1) was successfully engineered, expanding the toolkit for protein manipulation.
• The engineered domain facilitates a robust orthogonal affinity purification strategy, applicable to various target proteins.
• This work demonstrates the potential of protein engineering for creating versatile tools in biotechnology and bioprocessing.