A hybrid sequence approach to the paracelsus challenge

• Published in: Proteins, structure, function, and bioinformatics Vol. 30; no. 2; pp. 136 - 143
• Main Authors: Yuan, Shao-Min, Clarke, Neil D.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.02.1998
• Subjects: Amino Acid Sequence; circular dichroism; Cloning, Molecular; DNA-Binding Proteins; Models, Molecular; Molecular Sequence Data; Protein Denaturation; protein design; Protein Engineering; Protein Folding; protein structure; Protein Structure, Secondary; Proteins - chemistry; Recombinant Fusion Proteins - chemistry; Repressor Proteins - chemistry; trifluoroethanol; Trifluoroethanol - pharmacology; Viral Proteins - chemistry; Viral Regulatory and Accessory Proteins
• ISSN: 0887-3585; 1097-0134
• DOI: 10.1002/(SICI)1097-0134(19980201)30:2<136::AID-PROT3>3.0.CO;2-L

Inspired by the Paracelsus Challenge of Rose and Creamer (Proteins 19:1–3, 1994), we have designed a protein sequence that is 50% identical to an all‐helical protein but is intended to fold into a largely β‐sheet structure. Rather than attempt a de novo design, our strategy was to construct a hybrid sequence based on a helical “parent” protein (434 Cro) and a “target” protein with the desired fold (the B1 domain of protein G). The hybrid sequence (Crotein‐G) is 50% identical to 434 Cro but is also 62% identical to the B1 domain of protein G. We also created a variant of Crotein‐G (ZCrotein‐G) that contains a potential His3Cys1 zinc binding site. At low protein concentrations and in the presence of 20% 2,2,2‐trifluoroethanol (TFE) (v/v), the circular dichroism spectra of the designed proteins are distinct from that of 434 Cro and similar to that of the B1 domain of protein G. However, the proteins fail to denature in a cooperative manner. Furthermore, aggregation occurs at moderate protein concentrations or in the absence of TFE. Addition of zinc to ZCrotein‐G does not promote structure formation. In summary, 434 Cro has been altered to something that may resemble the B1 domain of protein G, but the protein does not adopt a native structure. Proteins 30:136–143, 1998. © 1998 Wiley‐Liss, Inc.