A ribonuclease S-peptide antagonist discovered with a bacteriophage display library.
From a filamentous phage library displaying random hexapeptides, we selected clones displaying peptides that bind S-protein, a 104-amino-acid (aa) fragment of bovine pancreatic ribonuclease (RNase). The selected peptides show a sequence motif, (F/Y)NF(E/V)(I/V)(L/V), that bears little resemblance to S-peptide, a 20-aa fragment of RNase that is S-protein's natural ligand. One of the displayed peptides, YNFEVL, was synthesized chemically and shown by isothermal titration calorimetry to bind S-protein with a dissociation equilibrium constant of 5.5 microM at 25 degrees C, an affinity comparable to that of previously studied S-peptide variants. The YNFEVL peptide is an antagonist of S-peptide, in that it blocks the ability of S-peptide to restore enzyme activity to S-protein. The S-protein/S-peptide system preserves the essential features of a pharmacologically significant receptor/hormone couple, and the S-peptide antagonist can therefore be regarded as a new RNase-specific 'drug'. This work illustrates the potential value of phage display libraries for discovering novel classes of pharmaceuticals.
Division of Biological Sciences, University of Missouri, Columbia 65211.
G P
GP
Smith
D A
DA
Schultz
J E
JE
Ladbury
D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000235:genetics*; D002151:Calorimetry; D015723:Gene Library; D007700:Kinetics; D008024:Ligands; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D012260:Ribonucleases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014961:X-Ray Diffraction
D008024:Ligands; D009842:Oligopeptides; D012260:Ribonucleases; C022542:ribonuclease S