Recombinant polypeptides comprising selenocysteine and method for producing the same

1. A nucleic acid molecule encoding a polypeptide comprising an amino acid sequence at least 90% identical to:

(a) SEQ ID NO:1 and having an amino acid substitution or deletion at a position corresponding to position 344 of SEQ ID NO:1;

(b) SEQ ID NO:2 and having an amino acid substitution or deletion at a position corresponding to position 702 of SEQ ID NO:2;

(c) SEQ ID NO:3 and having an amino acid substitution or deletion at a position corresponding to position 655 of SEQ ID NO:3;

(d) SEQ ID NO:4 and having an amino acid substitution or deletion at a position corresponding to position 73 of SEQ ID NO:4;

(e) SEQ ID NO:5 and having an amino acid substitution or deletion at a position corresponding to position 781 of SEQ ID NO:5;

(f) SEQ ID NO:6 and having an amino acid substitution or deletion at a position corresponding to position 136 of SEQ ID NO:6;

(g) SEQ ID NO:7 and having an amino acid substitution or deletion at a position corresponding to position 183 of SEQ ID NO:7;

(h) SEQ ID NO:8 and having an amino acid substitution or deletion at a position corresponding to position 1 of SEQ ID NO:8;

(i) SEQ ID NO:9 and having an amino acid substitution or deletion at a position corresponding to position 102 of SEQ ID NO:9;

(j) SEQ ID NO:10 and having an amino acid substitution or deletion at a position corresponding to position 105 of SEQ ID NO:10;

(k) SEQ ID NO:11 and having an amino acid substitution or deletion at a position corresponding to position 673 of SEQ ID NO:11;

(l) SEQ ID NO:12 and having an amino acid substitution or deletion at a position corresponding to position 69 of SEQ ID NO:12;

(m) SEQ ID NO:13 and having an amino acid substitution or deletion at a position corresponding to position 107 of SEQ ID NO:13;

(n) SEQ ID NO:17 and having an amino acid substitution or deletion at a position corresponding to position 246 of SEQ ID NO:17;

(o) SEQ ID NO:18 and having an amino acid substitution or deletion at a position corresponding to position 545 of SEQ ID NO:18; and/or

(p) SEQ ID NO:19 and having an amino acid substitution or deletion at a position corresponding to position 124 of SEQ ID NO:19.

2. A bacterial strain comprising at least one nucleic acid molecule selected from claim 1 .

3. The bacterial strain of claim 2 , wherein the bacterial strain is an E. coli strain.

4. The bacterial strain of claim 2 , comprising a nucleic acid that encodes a tRNA that is at least 90% identical to SEQ ID NO: 20 and comprising one or more of the following features:

(i) a G or C at a position corresponding to position 7;

(ii) a T at a position corresponding to position 49;

(iii) a A or C at a position corresponding to position 50;

(iv) a T at a position corresponding to position 64;

(v) a G or A at a position corresponding to position 65; and/or

(vi) a G, T or C at a position corresponding to position 66.

5. The bacterial strain of claim 4 , wherein the molecule encodes a tRNA comprising the sequence at least about 90% identical to SEQ ID NO: 20; and comprises one or more of the following features:

(i) a G at a position corresponding to position 7;

(ii) a T at a position corresponding to position 49;

(iii) a C at a position corresponding to position 50;

(iv) a T at a position corresponding to position 64;

(v) a G at a position corresponding to position 65; and/or

(vi) a C at a position corresponding to position 66.

6. The bacterial strain of claim 3 , wherein the strain is the E. coli bacterial strain deposited at the NCIMB under deposit Accession No. 42595.

7. A culture of bacteria comprising a bacterial strain in accordance with claim 2 .

8. The culture of claim 7 , said culture comprising an expressed recombinant polypeptide in an amount of 1 to 100 mg/L of the culture, said expressed recombinant polypeptide comprising at least one selenocysteine residue.

9. The culture of claim 8 , comprising an expressed recombinant polypeptide in an amount of 10 to 40 mg/L of the culture, said expressed recombinant polypeptide comprising at least one selenocysteine residue.

10. A method of expressing a polypeptide comprising at least one selenocysteine residue comprising:

(a) expressing a nucleic acid encoding the polypeptide in a bacterial strain according to claim 2 and in the presence of selenium source; and

(b) purifying the recombinant polypeptide from the bacteria.