Immunochemical Properties of Ribonuclease T₁ in Relation to Other Ribonucleases

Abstract

1. Antisera to RNase T₁ [EC 2. 7. 7. 26] can be prepared in rabbits by two methods: either by intravenous injection of alum-precipitated antigen on alternate days for 4 weeks or by intramuscular injection of antigen with Freund's complete adjuvant followed by the second injection of free antigen after 6 weeks.
2. The immunogenicity of RNase T₁ seems to be very weak. Thus, the content of antibody in the antisera obtained is less than that to RNase A [EC 2. 7. 7. 16].
3. The valence of antigen is estimated to be 4 at maximum.
4. Enzymatic activity of RNase T₁ assayed with RNA is completely inhibited by binding with antibody in antibody excess. However, assaying with a small molecular weight substrate, the enzymatic activity of washed immune precipitate is about 20% as great as that of RNase T₁ alone.
5. RNases T₂ and U₂ [EC 2. 7. 7. 17], with quite different substrate specificity from that of RNase T₁, and also RNase N₁, with qualitatively same specificity as that of RNase T₁, have no immunological relation to RNase T₁. But, RNase U₁ from Ustilago sphaerogena is found to be immunologically somewhat co-related to RNase T₁.