Cytotoxic ribonuclease variants
Cytotoxic variants of human ribonuclease 1 (RNase 1) identified through analysis of the interaction between RNase 1 and the human ribonuclease inhibitor (hRI) as defined by the three dimensional (3-D) atomic structure of the RNase1 hRI complex are disclosed. Also disclosed is the 3-D structure of the hRI·RNase 1 complex and methods for designing the RNase 1 variants.
1. An engineered human Ribonuclease (RNase 1) polypeptide only differing in amino acid sequence from an RNase 1 protein comprising SEQ ID NO:2 by at least four amino acid substitutions, the at least four amino acid substitutions consisting of:
(a) at least one amino acid substitution located within residues 85 to 94 of SEQ ID NO:2;
(b) the amino acid substitution G38R of SEQ ID NO:2; and
(c) at least two amino acid substitutions at amino acid residues selected from the group consisting of residues 4, 7, 11, 31, 32, 39, 41, 42, 66, 67, 71, 111 and 118 of SEQ ID NO:2.
2. The engineered RNase 1 polypeptide of claim 1 , wherein at least one of the amino acid substitutions located within residues 85 to 94 of SEQ ID NO: 2 is at an amino acid residue selected from the group consisting of residues 88, 89 and 91 of SEQ ID NO: 2.
3. The engineered RNase 1 polypeptide of claim 2 , wherein at least one of the amino acid substitutions located within residues 85 to 94 of SEQ ID NO:2 is selected from the group consisting of substitutions at residues 88 and 91 of SEQ ID NO:2.
4. The engineered RNase 1 polypeptide of claim 2 , wherein each of the amino acid substitutions located within residues 85 to 94 of SEQ ID NO:2 are at amino acid residues selected from the group consisting of residues 88, 89 and 91 of SEQ ID NO:2.
5. The engineered RNase 1 polypeptide of claim 4 , wherein the amino acid substitutions located within residues 85 to 94 of SEQ ID NO:2 consist of three amino acid substitutions at residues 88, 89, and 91 of SEQ ID NO:2.
6. The engineered RNase 1 polypeptide of claim 5 , wherein the difference in amino acid sequence from an RNase 1 protein comprising SEQ ID NO:2 consists of the following substitutions of SEQ ID NO:2:
R4C/G38R/R39G/N67R/N88L/G89R/R91G/V118C.
7. The engineered RNase 1 polypeptide of claim 4 , wherein the amino acid substitutions located within residues 85 to 94 of SEQ ID NO:2 consist of one amino acid substitution at residue 88 of SEQ ID NO:2.
8. The engineered RNase 1 polypeptide of claim 7 , wherein the amino acid substitutions at amino acid residues selected from the group consisting of residues 4, 7, 11, 31, 32, 39, 41, 42, 66, 67, 71, 111 and 118 of SEQ ID NO: 2 consist of two amino acid substitutions at residues 39 and 67 of SEQ ID NO: 2.
9. The engineered RNase 1 polypeptide of claim 8 , wherein the difference in amino acid sequence from an RNase 1 protein comprising SEQ ID NO:2 consists of the following substitutions of SEQ ID NO:2: G38R/R39G/N67R/N88R.