Studies on polypeptides XXXIII: Semisynthetic Ribonuclease analogues. The role of histidine‐119

Abstract As part of a structure‐activity relationship study of ribonuclease, focussing on the role of histidine‐119 in the active centre, two tetradecapeptides were synthesized by the solid‐phase method: [His119]RNase 111‐124 and the corresponding analogue in which His‐119 is replaced byL homohistidine. While the [Hhis119] analogue has almost the same binding capacity towards RNase 1‐118 protein as the natural peptide, the resulting complex is devoid of any catalytic activity when RNA or 2′,3′‐CMP is used as substrate.