Base Specificity and Primary Structure of Poly U-preferential Ribonuclease from Chicken Liver

The primary structure and base specificity of chicken liver RNase CL₁ which has been reported by Miura et al. [Chem. Pharm. Bull., 32,4053–4060 (1984)] as poly U-preferential RNase, were extensively studied. The sequence study of this enzyme and comparison of the amino acid sequence of the enzyme with homologous RNases from oyster and Drosophila melanogaster suggested that RNase CL₁ consists of three peptides with 17, 19, and 163 amino acid residues. The amino acid sequence of these three peptides were identified. The two small peptides are joined to the large peptide by disulfide bridges. The amino acid sequence of RNase CL₁ had 62 (31.2%) and 63 residues (31.6%) identical with oyster RNase and D. melanogaster RNase, respectively, and belongs to the RNase T₂ family RNase.

Reassessment of the base specificity of RNase CL₁ found that it is guanylic acid, then uridylic acid-preferential, and not poly U preferential.