Alternate protein frameworks for molecular recognition.
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.
Ku
J
J
Howard Hughes Medical Institute, University of California, Berkeley 94720, USA.
Schultz
P G
PG
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
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