title: Ribonuclease S-peptide. A model for molecular recognition.
abstract: The relationship of structure to function in the recognition of ribonuclease S-peptide by S-protein was studied by several methods. Liquid phase peptide synthesis was employed to generate analogs of S-peptide in which from 1 to 8 residues were deleted from the NH2-terminal end of the S-peptide. Additional derivatives were made by substitutions in the NH2-terminal three amino acids or by modifying the S-peptide analogs by trifluoroacetylation. The analogs were generated in the following way. S-Peptide was cleaved with chymotrypsin. The fragment obtained, RNase(9-20), was purified and lengthened step by step using liquid phase peptide synthesis. A second set of analogs were prepared by cleavage of CF3CO-S-peptide with elastase and the resulting CF3CO-RNase(7-20), similarly lengthened. The various analogs of S-peptide were tested in their capacity to combine with S-protein and regenerate biological activity as measured by Vmax and Kb. This work shows a positive contribution of every one of the first 8 NH2-terminal residues of S-peptide to the molecular recognition of S-protein in the presence of RNA substrate. Substitution of the first 3 residues by alanine or blocking of the free amino groups decreases recognition, indicating that the original primary structure is the most favorable one.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001665:Binding Sites; D002918:Chymotrypsin; D008433:Mathematics; D010196:Pancreatic Elastase; D011485:Protein Binding; D012260:Ribonucleases / Q000378:metabolism
chemical_list: D000596:Amino Acids; D012260:Ribonucleases; D002918:Chymotrypsin; D010196:Pancreatic Elastase