Disulfide bond substitution by directed evolution in an engineered binding protein.
Breaking ties: The antitumour protein, neocarzinostatin (NCS), is one of the few drug-carrying proteins used in human therapeutics. However, the presence of disulfide bonds limits this protein's potential development for many applications. This study describes a generic directed-evolution approach starting from NCS-3.24 (shown in the figure complexed with two testosterone molecules) to engineer stable disulfide-free NCS variants suitable for a variety of purposes, including intracellular applications.The chromoprotein neocarzinostatin (NCS) has been intensively studied for its antitumour properties. It has recently been redesigned as a potential drug-carrying scaffold. A potential limit of this protein scaffold, especially for intracellular applications, is the presence of disulfide bonds. The objective of this work was to create a disulfide-free NCS-derived scaffold. A generic targeted approach was developed by using directed evolution methods. As a starting point we used a previously engineered NCS variant in which a hapten binding site had been created. A library was then generated in which cysteine Cys88 and Cys93 and neighbouring residues were randomly substituted. Variants that preserved the hapten binding function were selected by phage display and further screened by colony filtration methods. Several sequences with common features emerged from this process. The corresponding proteins were expressed, purified and their biophysical properties characterised. How these selected sequences rescued folding ability and stability of the disulfide-free protein was carefully examined by using calorimetry and the results were interpreted with molecular simulation techniques.
Institut de Biochimie et Biophysique Moléculaire et Cellulaire, UMR 8619 CNRS, Université Paris Sud 11, 91405 Orsay cedex, France.
Antoine
A
Drevelle
Agathe
A
Urvoas
Mériam Ben
MB
Hamida-Rebaï
Gérard
G
Van Vooren
Magali
M
Nicaise
Marie
M
Valerio-Lepiniec
Michel
M
Desmadril
Charles H
CH
Robert
Philippe
P
Minard
D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000737:chemistry* / Q000378:metabolism; D001483:Base Sequence; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D019020:Directed Molecular Evolution; D004220:Disulfides / Q000737:chemistry*; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019151:Peptide Library; D011485:Protein Binding; D015202:Protein Engineering; D013739:Testosterone / Q000737:chemistry; D013816:Thermodynamics; D009353:Zinostatin / Q000737:chemistry* / Q000378:metabolism
D000970:Antineoplastic Agents; D004220:Disulfides; D050505:Mutant Proteins; D019151:Peptide Library; D013739:Testosterone; D009353:Zinostatin