title: Kinetic and conformational studies on some partially synthetic ribonuclease S' analogues modified in position 8.
abstract: Syntheses are described of two S-peptide analogues where the arginyl residue in position 10 has been replaced by ornithine and the phenylalanine in position 8 has been substituted by the unnatural amino acids cyclohexylalanine or p-fluorophenylalanine. In order to regenerate the arginyl residue, which is present in position 10 in the natural sequence, the S-peptide analogues beloning to the [Orn10]-series are transformed into the corresponding guanidinated derivatives by treatment with O-methylisourea. 1epsilon, 7epsilon, 10delta triguan-[Cha8, Orn10]-, 1epsilon, 7epsilon, 10delta-triguan-[pF-Phe8, Orn10]- and 1epsilon, 7epsilon, 10delta-triguan-[Tyr8, Orn10]-S-peptides were prepared. The ability to bind to and activate the S-protein of the synthetic S-peptide analogues, before and after guanidination, was tested by exploring their capacity to generate ribonuclease activity using RNA and C greater than p as substrates. The affinity of the different peptides for the S-protein in the absence of substrate was evaluated by difference spectroscopy.
mesh_terms: D000595:Amino Acid Sequence; D001681:Biological Assay; D006146:Guanidines; D008968:Molecular Conformation; D010455:Peptides / Q000138:chemical synthesis; D012260:Ribonucleases / Q000032:analysis* / Q000138:chemical synthesis
chemical_list: D006146:Guanidines; D010455:Peptides; D012260:Ribonucleases