title: Consolidating critical binding determinants by noncyclic rearrangement of protein secondary structure.
abstract: We designed a single-chain variant of the Arc repressor homodimer in which the beta strands that contact operator DNA are connected by a hairpin turn and the alpha helices that form the tetrahelical scaffold of the dimer are attached by a short linker. The designed protein represents a noncyclic permutation of secondary structural elements in another single-chain Arc molecule (Arc-L1-Arc), in which the two subunits are fused by a single linker. The permuted protein binds operator DNA with nanomolar affinity, refolds on the sub-millisecond time scale, and is as stable as Arc-L1-Arc. The crystal structure of the permuted protein reveals an essentially wild-type fold, demonstrating that crucial folding information is not encoded in the wild-type order of secondary structure. Noncyclic rearrangement of secondary structure may allow grouping of critical active-site residues in other proteins and could be a useful tool for protein design and minimization.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Ramon K
authors.initials: RK
authors.lastname: Tabtiang
authors.forename: Brent O
authors.initials: BO
authors.lastname: Cezairliyan
authors.forename: Robert A
authors.initials: RA
authors.lastname: Grant
authors.forename: Jesse C
authors.initials: JC
authors.lastname: Cochrane
authors.forename: Robert T
authors.initials: RT
authors.lastname: Sauer
mesh_terms: D017100:Bacteriophage P22 / Q000737:chemistry / Q000235:genetics; D018360:Crystallography, X-Ray; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D011485:Protein Binding; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D004279:DNA, Viral; D011994:Recombinant Proteins; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins