The invention relates to a method of making a polypeptide comprising an orthogonal functional group, said orthogonal functional group being comprised by an aliphatic amino acid or amino acid derivative, said method comprising providing a host cell; providing a nucleic acid encoding the polypeptide of interest; providing a tRNA-tRNA synthetase pair orthogonal to said host cell; adding an amino acid or amino acid derivative comprising the orthogonal functional group of interest, wherein said amino acid or amino acid derivative is a substrate for said orthogonal tRNA synthetase, wherein said amino acid or amino acid derivative has an aliphatic carbon backbone; and incubating to allow incorporation of said amino acid or amino acid derivative into the polypeptide of interest via the orthogonal tRNA-tRNA synthetase pair. The invention also relates to certain amino acids, and to polypeptides comprising same.
1. A method of making a polypeptide comprising an orthogonal functional group, said orthogonal functional group being comprised by an aliphatic amino acid comprising an alkyne group or an azide group, wherein said aliphatic amino acid does not comprise an aromatic moiety, said method comprising providing a host cell; providing a nucleic acid encoding the polypeptide of interest; providing a tRNA-tRNA synthetase pair orthogonal to said host cell; adding said amino acid comprising the orthogonal functional group of interest, wherein said amino acid is a substrate for said orthogonal tRNA synthetase and incubating to allow incorporation of said amino acid into the polypeptide of interest via the orthogonal tRNA-tRNA synthetase pair.
2. A method according to claim 1 wherein incorporation is mediated by an amber codon specified by said nucleic acid.
3. A method according to claim 1 wherein the amino acid is or is derived from lysine.
4. A method according to claim 1 wherein the orthogonal tRNA-tRNA synthetase pair are a cognate pair capable of acting on pyrrolysine.
5. A method according to claim 1 wherein the orthogonal tRNA-tRNA synthetase pair have sequences identical to the wild type sequences of the organism in which they naturally occur.
6. A method according to claim 4 wherein the tRNA-tRNA synthetase pair is MbtRNA CUA and MbPyIRS.
7. A method according to claim 6 wherein the MbtRNA CUA comprises the nucleotide sequence of SEQ ID NO:3 and the MbPyIRS comprises the amino acid sequence of SEQ ID NO:1.
8. A method according to claim 1 wherein the host cell is E. coli.
9. A method according to claim 1 wherein said tRNA synthetase is a tRNA synthetase having the amino acid sequence of SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10 or SEQ ID NO:12.
10. A method according to claim 1 wherein said tRNA synthetase is encoded by a nucleic acid comprising the nucleotide sequence of SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11 or SEQ ID NO:13.
11. A method according to claim 5 wherein the tRNA-tRNA synthetase pair is MbtRNA CUA and MbPyIRS.
12. A method according to claim 11 wherein the MbtRNA CUA comprises the nucleotide sequence of SEQ ID NO:3 and the MbPyIRS comprises the amino acid sequence of SEQ ID NO:1.
13. A method according to claim 1 wherein the functional group comprises an azide group.
14. A method of making a polypeptide comprising an orthogonal functional group, said orthogonal functional group being comprised by an aliphatic amino acid comprising an alkyne group or an azide group, wherein the aliphatic amino acid does not comprise an aromatic moiety, said method comprising providing a host cell; providing a nucleic acid encoding the polypeptide of interest; providing a tRNA-tRNA synthetase pair orthogonal to said host cell, wherein said orthogonal tRNA-tRNA synthetase pair have sequences identical to the wild type sequences of the organism in which they naturally occur; adding said amino acid comprising the orthogonal functional group of interest, wherein said amino acid is a substrate for said orthogonal tRNA synthetase and incubating to allow incorporation of said amino acid into the polypeptide of interest via the orthogonal tRNA-tRNA synthetase pair.