Structure-based substitutions for increased solubility of a designed protein.
Manipulation of protein solubility is important for many aspects of protein design and engineering. Previously, we designed a series of consensus ankyrin repeat proteins containing one, two, three and four identical repeats (1ANK, 2ANK, 3ANK and 4ANK). These proteins, particularly 4ANK, are intended for use as a universal scaffold on which specific binding sites can be constructed. Despite being well folded and extremely stable, 4ANK is soluble only under acidic conditions. Designing interactions with naturally occurring proteins requires the designed protein to be soluble at physiological pH. Substitution of six leucines with arginine on exposed hydrophobic patches on the surface of 4ANK resulted in increased solubility over a large pH range. Study of the pH dependence of stability demonstrated that 4ANK is one of the most stable ankyrin repeat proteins known. In addition, analogous leucine to arginine substitutions on the surface of 2ANK allowed the partially folded protein to assume a fully folded conformation. Our studies indicate that replacement of surface-exposed hydrophobic residues with positively charged residues can significantly improve protein solubility at physiological pH.
Mosavi
Leila K
LK
Department of Biochemistry, University of Connecticut Health Center, Farmington, CT 06032, USA.
Peng
Zheng-Yu
ZY
D019943:Amino Acid Substitution / Q000235:genetics*; D017089:Ankyrin Repeat; D001120:Arginine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000235:genetics*; D012995:Solubility; D013329:Structure-Activity Relationship; D013816:Thermodynamics
D011506:Proteins; D001120:Arginine