Nuclease properties of two putative zinc finger peptides

We studied the interaction of wheat germ 5S rRNA with synthetic polypeptides whose amino acid sequences were similar to that of the second zinc finger of Xenopus laevis transcriptional factor IIIA (TFIIIA). The results clearly show that in addition to weak 5S rRNA binding activity (data not shown), these two 30 amino acid long polypeptides hydrolyse some phosphodiester bonds of wheat germ 5S rRNA. The cleavage pattern of plant 5S rRNA is very specific and the cuts occur only after the pyrimidine residues. The same properties of these peptides were furthermore observed for E. coli tRNA(Phe). We found that the digestion specificity of both the zinc finger peptides is very similar to that of a pancreatic ribonuclease (RNase A).