Applicability of Arginyl-tRNA: Protein Arginyltransferase in Peptide Synthesis

A monoclonal antibody (MAb 1C3) to bovine β-casein was prepared, and a peptide (from 184 to 202 residues of β-casein) that could bind this monoclonal antibody was separated from a tryptic digest of β-casein. Other β-casein fragments, the peptide from 193 to 202 and the one from 1 to 189 residues, were also prepared for comparison. MAb 1C3 belongs to the IgG₁ subclass with a κ chain and its pI was 5.9. The binding affinity of β-casein and β-casein fragments to the monoclonal antibody was investigated by a competitive radioimmunoassay, and the order of affinity was β-casein peptide from 193 to 202 > β-casein > β-casein peptide from 184 to 202 > β-casein peptide from 1 to 189. On the basis of the results, the mechanism for the interaction between MAb 1C3 and β-casein fragments is discussed.