Table 1.

Relationship between peptide structure and RNA cleavage activity for the wild-type and mutant peptides

Peptide	Initial Rate (V0) pM⋅min−1*	Structure	Sequence
ZN⋅ZFY-6	Below detection limit	Monomer	KTYQCQYCEYRSADSSNLKTHIKTKHSKEK
ZFY-6	6000  ±  130	Dimer	KTYQCQYCEYRSADSSNLKTHIKTKHSKEK
E9A	1800  ±   90	Dimer	KTYQCQYCAYRSADSSNLKTHIKTKHSKEK
H21,26A	800  ±   30	Dimer	KTYQCQYCEYRSADSSNLKTAIKTKASKEK
C5,8A	Below detection limit	Monomer	KTYQAQYAEYRSADSSNLKTHIKTKHSKEK
Reduced ZFY-6	Below detection limit	Monomer	KTYQAQYAEYRSADSSNLKTAIKTKASKEK

The initial cleavage rates for the various peptides were determined with the (ACUCCACCAUAGUACACUCC) RNA substrate. Mutant peptides exhibiting ribonuclease activity hydrolyzed the RNA substrate at the same positions observed for the ZFY-6 dimer (see Table 2). Underlined residues indicate the position of the alanine-substituted amino acids within the mutant peptide sequence. 

^*Detection limit = cleavage rates resulting in <1% of the RNA substrate cleaved over 60 min.