title: Alternate protein frameworks for molecular recognition.
abstract: In an effort to determine whether proteins with structures other than the immunoglobulin fold can be used to mimic the ligand binding properties of antibodies, we generated a library from the four-helix bundle protein cytochrome b562 in which the two loops were randomized. Panning of this library against the bovine serum albumin (BSA) conjugate of N-methyl-p-nitrobenzylamine derivative 1 by phage display methods yielded cytochromes in which residues Trp-20, Arg-21, and Ser-22 in loop A and Arg-83 and Trp-84 in loop B were conserved. The individual mutants, which fold into native-like structure, bind selectively to the BSA-1 conjugate with micromolar dissociation constants (Kd), in comparison to a monoclonal antibody that binds selectively to 1 with a Kd of 290 nM. These and other antibody-like receptors may prove useful as therapeutic agents or as reagents for both intra- and extracellular studies.
authors.affiliation: Howard Hughes Medical Institute, University of California, Berkeley 94720, USA.
authors.forename: J
authors.initials: J
authors.lastname: Ku
authors.forename: P G
authors.initials: PG
authors.lastname: Schultz
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine; D001435:Bacteriophages; D001483:Base Sequence; D002942:Circular Dichroism; D017124:Conserved Sequence; D003573:Cytochrome b Group / Q000096:biosynthesis* / Q000737:chemistry*; D016208:Databases, Factual; D004797:Enzyme-Linked Immunosorbent Assay; D029968:Escherichia coli Proteins; D005822:Genetic Vectors; D006422:Hemerythrin / Q000031:analogs & derivatives / Q000096:biosynthesis / Q000737:chemistry; D008961:Models, Structural; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D014176:Protein Biosynthesis; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D011897:Random Allocation; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D012694:Serine; D012710:Serum Albumin, Bovine; D014364:Tryptophan
chemical_list: D003573:Cytochrome b Group; D029968:Escherichia coli Proteins; D006422:Hemerythrin; D009838:Oligodeoxyribonucleotides; D011506:Proteins; D011994:Recombinant Proteins; C008571:myohemerythrin; D012710:Serum Albumin, Bovine; D012694:Serine; D014364:Tryptophan; C017850:cytochrome b562, E coli; D001120:Arginine