Covalent tethering of functional groups to proteins and substrates therefor
View Patent ↗A mutant hydrolase optionally fused to a protein of interest is provided. The mutant hydrolase is capable of forming a bond with a substrate for the corresponding nonmutant (wild-type) hydrolase which is more stable than the bond formed between the wild-type hydrolase and the substrate and has at least two amino acid substitutions relative to the wild-type hydrolase. Substrates for hydrolases comprising one or more functional groups are also provided, as well as methods of using the mutant hydrolase and the substrates of the invention. Also provided is a fusion protein capable of forming a stable bond with a substrate and cells which express the fusion protein.
1. A polynucleotide comprising a nucleic acid sequence encoding a mutant of the dehalogenase of SEQ ID NO: 82, the mutant having at least 85% sequence identity to SEQ ID NO: 82, and the mutant comprising at least two amino acid substitutions, wherein the mutant dehalogenase forms a bond with a dehalogenase substrate which comprises one or more functional groups, which bond is more stable than the bond formed between the dehalogenase of SEQ ID NO: 82 and the substrate, wherein at least one amino acid substitution in the mutant dehalogenase is a substitution at an amino acid residue corresponding to residue 272 of SEQ ID NO:82, a residue that is associated with activating a water molecule which cleaves the bond formed between the corresponding wild-type dehalogenase and the substrate, and wherein a second substitution is at an amino acid residue corresponding to residue 175 in the Rhodococcus dehalogenase having the amino acid sequence of SEQ ID NO:82.
2. The polynucleotide of claim 1 which encodes SEQ ID NO:81.
3. The polynucleotide of claim 1 wherein the second substitution is to an amino acid which introduces one or more charges, introduces one or more hydrogen bonds, or reduces steric hindrance, thereby enhancing substrate binding.
4. The polynucleotide of claim 1 , wherein the substituted amino acid at the position corresponding to amino acid residue 272 is phenylalanine, glycine or alanine.
5. The polynucleotide of claim 1 wherein the substituted amino acid at the position corresponding to amino acid residue 175 is methionine, valine, glutamate, aspartate, alanine, leucine, serine or cysteine.
6. The polynucleotide of claim 1 further comprising a third and optionally a fourth substitution at an amino acid residue in the corresponding wild-type dehalogenase that is within the active site cavity and within 3 to 5 Å of a dehalogenase substrate bound to the mutual dehalogenase.
7. The polynucleotide of claim 6 wherein the third substitution or third and fourth substitutions are at a position corresponding to amino acid residue 176 or 273 of a Rhodococcus rhodochrous dehalogenase.
8. The polynucleotide of claim 7 wherein the substituted amino acid at the position corresponding to amino acid residue 176 is serine, glycine, asparagine, aspartate, threonine, alanine or arginine, or wherein the substituted amino acid at the position corresponding to amino acid residue 273 is leucine, methionine or cysteine.
9. The polynucleotide of claim 1 wherein the nucleic acid sequence further comprises an open reading frame for one or more proteins of interest, thereby yielding a fusion protein.
10. A method of making a mutant dehalogenase polypeptide encoded by the polynucleotide of claim 1 , comprising expressing the polynucleotide of claim 1 in a host cell so as to express the mutant dehalogenase.
11. The method of claim 10 wherein the host cell is a bacterial cell.
12. The method of claim 10 wherein the host cell is a mammalian cell.
13. A method of making a mutant dehalogenase polypeptide encoded by the polynucleotide of claim 1 , comprising translating RNA corresponding to the polynucleotide of claim 1 in a cell free protein expression system.
14. The polynucleotide of claim 6 wherein the third and fourth substitutions are at positions corresponding to amino acid residues 176 and 273 of a Rhodococcus rhodochrous dehalogenase.
15. The polynucleotide of claim 14 wherein the substituted amino acid at the position corresponding to amino acid residue 176 is serine, glycine, asparagine, aspartate, threonine, alanine or arginine, and the substituted amino acid a the position corresponding to amino acid residue 273 is leucine, methionine or cysteine.