Artificially enhanced bacteria capable of producing new synthetic chemicals

For the first time, the scientists in salk's institute of biological science have developed the new strain which can able to produce the new synthetic chemicals by incorporating the unnatural aminoacids in the biological building blocks. Lei Wang, assistant professor in Salk's Chemical Biology and Proteomics Laboratory, and his team developed this strain.
In this study first they have made the UAG stop codon as a blank codon by removing the gene that produces RF1, because the RF1 is resposible to recognize this UAG stop codon but this RF1 release factor is important for the E.coli to survive. Then,they altered production of release factor 2 (RF2), so that it could rescue the engineered bacterium. In the place of every UAG stop codon they have introduced the unnatural aminoacids with the help of UAG decoding orthogonal t-RNA synthetase pair.

The result was a strain of bacteria capable of efficiently producing proteins containing Uaas at multiple places. These synthetic molecules give promise to produce the proteins which contains the unnatural amino acids along with the naturally occuring aminoacids which will give the opening to produce new drugs. This is the new opening in the field of protein engineering.

The study of expanded genetic code is really interesting and you can read a lot more in the paper published by the same group in 2001 and 2007 on incorporating unnatural aminoacids.

Journal Reference:
David B F Johnson, Jianfeng Xu, Zhouxin Shen, Jeffrey K Takimoto, Matthew D Schultz, Robert J Schmitz, Zheng Xiang, Joseph R Ecker, Steven P Briggs, Lei Wang. RF1 knockout allows ribosomal incorporation of unnatural amino acids at multiple sites. Nature Chemical Biology, 2011; DOI: 10.1038/nchembio.657