Stability towards alkaline conditions can be engineered into a protein ligand

One of the problems with a proteinaceous affinity ligand is their sensitivi ty to alkaline conditions. Here, we show that a simple and straightforward strategy consisting of replacing all asparagine residues with other amino a cids can dramatically improve the chemical stability of a protein towards a lkaline conditions. As a model, a Streptococcal albumin-binding domain (ABD ) was used. The engineered variant showed higher stability towards 0.5 M Na OH, as well as higher thermal stability compared to its native counterpart. This protein engineering approach could potentially also be used for other protein ligands to eliminate the sensitivity to alkaline cleaning-in-place (CIP) conditions. (C) 2000 Elsevier Science B.V. All rights reserved.