Expanded blueprint: Genetic incorporation of two different noncanonic amino acids into one protein

Apr 15, 2010

(PhysOrg.com) -- The genetic code includes information for only 20 amino acids (AAs). If this repertoire could be expanded, it would, for example, be possible to program bacteria to produce tailored proteins with various characteristics of interest to science, technology, or medicine.

In fact, the natural protein-production mechanism can be reprogrammed, but until now it has only been possible to incorporate a single new type of AA into a . Wenshe Liu and his co-workers at Texas A&M University (USA) have now successfully included two different, noncanonic into the genetic material of , as they report in the journal Angewandte Chemie.

In order to synthesize a protein, a cell first copies a “blueprint” (mRNA) from the corresponding gene and “reads” it (translation). The for every AA consists of three “letters” (nucleotides). In addition, there is a start codon and three different codons that mean “stop”. “Transporters” (tRNA) that specifically recognize the codons are loaded with the required AA and bring it to the place where protein synthesis occurs (ribosomes). The “loaders” are special enzymes (aminoacyl tRNA synthetases).

Only 20 AAs are naturally coded; these are known as the canonical AAs. Other AAs are made accessible to organisms by modification of individual AAs in the finished protein at a later stage. However, some bacteria that require an unusual AA as part of an enzyme used in their metabolism of methane use one of their stop codons (amber) for another purpose, so it functions as a codon for the additional AA. This method has previously been successfully emulated in the laboratory. Liu and his teams have now for the first time used two such bacterial systems in parallel. One of the tRNAs was mutated to recognize a different stop codon (ochre). By mutation, they were able to reprogram the associated aminoacyl tRNA synthetases so that they load up their tRNAs with the desired synthetic AA.

The researchers incorporated this altered genetic material into bacterial cells. As desired, these cells then incorporated two noncanonical AAs into one protein. These two AAs are constructed so that each has a specific “snap” where desired functional groups can later simply be “clicked on” (click chemistry). For example, it is possible to attach special pairs of molecules that fluoresce when they can exchange energy with each other. To do this, they must be at a specific distance and angle relative to each other. Such pairs make it possible to draw conclusions about the conformation of a protein, as well as its dynamic changes during a reaction.

Explore further: Chemical biologists find new halogenation enzyme

More information: Wenshe Liu, A Facile System for Genetic Incorporation of Two Different Noncanonical Amino Acids into One Protein in Escherichia coli, Angewandte Chemie International Edition 2010, 49, No. 18, 3211-3214, dx.doi.org/10.1002/anie.201000465

add to favorites email to friend print save as pdf

Related Stories

New compound effectively treats fungal infections

Jun 22, 2007

A new mechanism to attack hard-to-treat fungal infections has been revealed by scientists from the biotech company Anacor Pharmaceuticals Inc., California, and the European Molecular Biology Laboratory (EMBL) outstation in ...

Model suggests how life's code emerged from primordial soup

Aug 07, 2009

(PhysOrg.com) -- In 1953, Stanley Miller filled two flasks with chemicals assumed to be present on the primitive Earth, connected the flasks with rubber tubes and introduced some electrical sparks as a stand-in for lightning. ...

Recommended for you

Chemical biologists find new halogenation enzyme

Sep 15, 2014

Molecules containing carbon-halogen bonds are produced naturally across all kingdoms of life and constitute a large family of natural products with a broad range of biological activities. The presence of halogen substituents ...

Protein secrets of Ebola virus

Sep 15, 2014

The current Ebola virus outbreak in West Africa, which has claimed more than 2000 lives, has highlighted the need for a deeper understanding of the molecular biology of the virus that could be critical in ...

Protein courtship revealed through chemist's lens

Sep 15, 2014

Staying clear of diseases requires that the proteins in our cells cooperate with one another. But, it has been a well-guarded secret how tens of thousands of different proteins find the correct dancing partners ...

Decoding 'sweet codes' that determine protein fates

Sep 15, 2014

We often experience difficulties in identifying the accurate shape of dynamic and fluctuating objects. This is especially the case in the nanoscale world of biomolecules. The research group lead by Professor Koichi Kato of ...

User comments : 0